diff --git a/lib/compiler.ts b/lib/compiler.ts
index de75edb0..5df1bdbb 100644
--- a/lib/compiler.ts
+++ b/lib/compiler.ts
@@ -33,7 +33,7 @@ export class ProjectCompiler implements ICompiler {
 	finalTransformers: FinalTransformers;
 	host: Host;
 	project: ProjectInfo;
-	program: ts.Program;
+	program: ts.BuilderProgram;
 	private hasSourceMap: boolean;
 
 	prepare(project: ProjectInfo, finalTransformers?: FinalTransformers) {
@@ -68,24 +68,21 @@ export class ProjectCompiler implements ICompiler {
 			rootFilenames.map(fileName => this.project.input.getFile(fileName).gulp.cwd)
 		);
 
-		this.host = new Host(
-			this.project.typescript,
-			currentDirectory,
-			this.project.input,
-			this.project.options
-		);
-
-		// Calling `createProgram` with an object is only supported in 3.0. Only call this overload
-		// if we have project references (also only supported in 3.0)
-		this.program = this.project.projectReferences
-			? this.project.typescript.createProgram({
+		if (this.program === undefined) {
+			this.host = new Host(
+				this.project.typescript,
+				currentDirectory,
+				this.project.input,
+				this.project.options
+			);
+			this.program = this.project.typescript.createIncrementalProgram({
 				rootNames: rootFilenames,
 				options: this.project.options,
 				projectReferences: this.project.projectReferences,
 				host: this.host,
-				oldProgram: this.program
-			})
-			: this.project.typescript.createProgram(rootFilenames, this.project.options, this.host, this.program);
+				createProgram: this.project.typescript.createAbstractBuilder
+			});
+		}
 
 		const result = emptyCompilationResult(this.project.options.noEmit);
 
@@ -178,7 +175,7 @@ export class ProjectCompiler implements ICompiler {
 			callback,
 			undefined,
 			false,
-			this.finalTransformers ? this.finalTransformers(this.program) : undefined,
+			this.finalTransformers ? this.finalTransformers(this.program.getProgram()) : undefined,
 		);
 		result.emitSkipped = emitOutput.emitSkipped;
 
diff --git a/lib/host.ts b/lib/host.ts
index 6408f7ec..de60a00c 100644
--- a/lib/host.ts
+++ b/lib/host.ts
@@ -81,7 +81,10 @@ export class Host implements ts.CompilerHost {
 		let sourceFile = this.input.getFile(fileName);
 		if (sourceFile) return sourceFile.ts;
 
-		return this.fallback.getSourceFile(fileName, languageVersion, onError);
+		const file = this.fallback.getSourceFile(fileName, languageVersion, onError);
+		if (file === undefined) return undefined;
+		(file as any).version = this.input.versionString;
+		return file;
 	}
 
 	realpath = (path: string) => this.fallback.realpath(path);
@@ -91,5 +94,7 @@ export class Host implements ts.CompilerHost {
 	directoryExists = (path: string) => this.fallback.directoryExists(path);
 
 	readDirectory = (rootDir: string, extensions: string[], excludes: string[], includes: string[], depth?: number) => 
-		this.fallback.readDirectory(rootDir, extensions, excludes, includes, depth)
+		this.fallback.readDirectory(rootDir, extensions, excludes, includes, depth);
+
+	createHash = (data: string) => this.fallback.createHash(data);
 }
diff --git a/lib/input.ts b/lib/input.ts
index 61d87ae4..4127d832 100644
--- a/lib/input.ts
+++ b/lib/input.ts
@@ -156,10 +156,11 @@ export class FileCache {
 	current: FileDictionary;
 	options: ts.CompilerOptions;
 	caseSensitive: boolean;
-	noParse: boolean = false; // true when using a file based compiler.
+	noParse = false; // true when using a file based compiler.
 
 	typescript: typeof ts;
-	version: number = 0;
+	version = 0;
+	versionString = "0";
 
 	constructor(typescript: typeof ts, options: ts.CompilerOptions, caseSensitive: boolean) {
 		this.typescript = typescript;
@@ -177,6 +178,7 @@ export class FileCache {
 
 	reset() {
 		this.version++;
+		this.versionString = this.version.toString();
 		this.previous = this.current;
 		this.createDictionary();
 	}
@@ -196,6 +198,7 @@ export class FileCache {
 			}
 		}
 		file.ts = this.typescript.createSourceFile(file.fileNameOriginal, file.content, this.options.target);
+		(file.ts as any).version = this.versionString;
 	}
 
 	getFile(name: string) {
diff --git a/release/compiler.d.ts b/release/compiler.d.ts
index 266f7216..1f9b5615 100644
--- a/release/compiler.d.ts
+++ b/release/compiler.d.ts
@@ -15,7 +15,7 @@ export declare class ProjectCompiler implements ICompiler {
     finalTransformers: FinalTransformers;
     host: Host;
     project: ProjectInfo;
-    program: ts.Program;
+    program: ts.BuilderProgram;
     private hasSourceMap;
     prepare(project: ProjectInfo, finalTransformers?: FinalTransformers): void;
     inputFile(file: File): void;
diff --git a/release/compiler.js b/release/compiler.js
index 5b3f1c4c..7f11f72d 100644
--- a/release/compiler.js
+++ b/release/compiler.js
@@ -33,18 +33,16 @@ class ProjectCompiler {
         }
         this.project.options.sourceMap = this.hasSourceMap;
         const currentDirectory = utils.getCommonBasePathOfArray(rootFilenames.map(fileName => this.project.input.getFile(fileName).gulp.cwd));
-        this.host = new host_1.Host(this.project.typescript, currentDirectory, this.project.input, this.project.options);
-        // Calling `createProgram` with an object is only supported in 3.0. Only call this overload
-        // if we have project references (also only supported in 3.0)
-        this.program = this.project.projectReferences
-            ? this.project.typescript.createProgram({
+        if (this.program === undefined) {
+            this.host = new host_1.Host(this.project.typescript, currentDirectory, this.project.input, this.project.options);
+            this.program = this.project.typescript.createIncrementalProgram({
                 rootNames: rootFilenames,
                 options: this.project.options,
                 projectReferences: this.project.projectReferences,
                 host: this.host,
-                oldProgram: this.program
-            })
-            : this.project.typescript.createProgram(rootFilenames, this.project.options, this.host, this.program);
+                createProgram: this.project.typescript.createAbstractBuilder
+            });
+        }
         const result = reporter_1.emptyCompilationResult(this.project.options.noEmit);
         const optionErrors = this.program.getOptionsDiagnostics();
         const syntaxErrors = this.program.getSyntacticDiagnostics();
@@ -73,22 +71,24 @@ class ProjectCompiler {
             const output = {};
             const input = this.host.input.getFileNames(true);
             for (let i = 0; i < input.length; i++) {
-                const fileName = utils.normalizePath(input[i]);
+                const fileName = this.host.getCanonicalFileName(input[i]);
                 const file = this.project.input.getFile(fileName);
                 output[fileName] = { file };
             }
             this.emit(result, preEmitDiagnostics, (fileName, content, writeByteOrderMark, onError, sourceFiles) => {
+                if (sourceFiles === undefined)
+                    return; // .tsbuildinfo file, ignore
                 if (sourceFiles.length !== 1) {
                     throw new Error("Failure: sourceFiles in WriteFileCallback should have length 1, got " + sourceFiles.length);
                 }
-                const fileNameOriginal = utils.normalizePath(sourceFiles[0].fileName);
+                const fileNameOriginal = this.host.getCanonicalFileName(sourceFiles[0].fileName);
                 const file = output[fileNameOriginal];
                 if (!file)
                     return;
                 this.attachContentToFile(file, fileName, content);
             });
             for (let i = 0; i < input.length; i++) {
-                const fileName = utils.normalizePath(input[i]);
+                const fileName = this.host.getCanonicalFileName(input[i]);
                 this.emitFile(output[fileName], currentDirectory);
             }
         }
@@ -116,7 +116,7 @@ class ProjectCompiler {
         }
     }
     emit(result, preEmitDiagnostics, callback) {
-        const emitOutput = this.program.emit(undefined, callback, undefined, false, this.finalTransformers ? this.finalTransformers(this.program) : undefined);
+        const emitOutput = this.program.emit(undefined, callback, undefined, false, this.finalTransformers ? this.finalTransformers(this.program.getProgram()) : undefined);
         result.emitSkipped = emitOutput.emitSkipped;
         // `emitOutput.diagnostics` might contain diagnostics that were already part of `preEmitDiagnostics`.
         // See https://github.com/Microsoft/TypeScript/issues/20876
@@ -130,8 +130,6 @@ class ProjectCompiler {
         }
     }
     emitFile({ file, jsFileName, dtsFileName, dtsMapFileName, jsContent, dtsContent, dtsMapContent, jsMapContent }, currentDirectory) {
-        if (!jsFileName)
-            return;
         let base;
         let baseDeclarations;
         if (file) {
@@ -153,7 +151,9 @@ class ProjectCompiler {
         else {
             base = this.project.directory;
             baseDeclarations = base;
-            jsFileName = path.resolve(base, jsFileName);
+            if (jsFileName !== undefined) {
+                jsFileName = path.resolve(base, jsFileName);
+            }
             if (dtsFileName !== undefined) {
                 dtsFileName = path.resolve(base, dtsFileName);
             }
diff --git a/release/host.d.ts b/release/host.d.ts
index 85ccf367..51b78334 100644
--- a/release/host.d.ts
+++ b/release/host.d.ts
@@ -20,4 +20,5 @@ export declare class Host implements ts.CompilerHost {
     getDirectories: (path: string) => string[];
     directoryExists: (path: string) => boolean;
     readDirectory: (rootDir: string, extensions: string[], excludes: string[], includes: string[], depth?: number) => string[];
+    createHash: (data: string) => string;
 }
diff --git a/release/host.js b/release/host.js
index e2d05870..96187121 100644
--- a/release/host.js
+++ b/release/host.js
@@ -24,12 +24,17 @@ class Host {
             let sourceFile = this.input.getFile(fileName);
             if (sourceFile)
                 return sourceFile.ts;
-            return this.fallback.getSourceFile(fileName, languageVersion, onError);
+            const file = this.fallback.getSourceFile(fileName, languageVersion, onError);
+            if (file === undefined)
+                return undefined;
+            file.version = this.input.versionString;
+            return file;
         };
         this.realpath = (path) => this.fallback.realpath(path);
         this.getDirectories = (path) => this.fallback.getDirectories(path);
         this.directoryExists = (path) => this.fallback.directoryExists(path);
         this.readDirectory = (rootDir, extensions, excludes, includes, depth) => this.fallback.readDirectory(rootDir, extensions, excludes, includes, depth);
+        this.createHash = (data) => this.fallback.createHash(data);
         this.typescript = typescript;
         this.fallback = typescript.createCompilerHost(options);
         this.currentDirectory = currentDirectory;
@@ -39,10 +44,10 @@ class Host {
         return '\n';
     }
     useCaseSensitiveFileNames() {
-        return false;
+        return this.fallback.useCaseSensitiveFileNames();
     }
     getCanonicalFileName(filename) {
-        return utils.normalizePath(filename);
+        return utils.normalizePath(this.useCaseSensitiveFileNames(), filename);
     }
     getDefaultLibFileName(options) {
         return this.fallback.getDefaultLibFileName(options);
diff --git a/release/input.d.ts b/release/input.d.ts
index 805f34c2..2196efde 100644
--- a/release/input.d.ts
+++ b/release/input.d.ts
@@ -26,16 +26,17 @@ export interface File {
     ts?: ts.SourceFile;
 }
 export declare module File {
-    function fromContent(fileName: string, content: string): File;
-    function fromGulp(file: VinylFile): File;
+    function fromContent(caseSensitive: boolean, fileName: string, content: string): File;
+    function fromGulp(caseSensitive: boolean, file: VinylFile): File;
     function equal(a: File, b: File): boolean;
     function getChangeState(previous: File, current: File): FileChangeState;
 }
 export declare class FileDictionary {
     files: utils.Map<File>;
     firstSourceFile: File;
+    caseSensitive: boolean;
     typescript: typeof ts;
-    constructor(typescript: typeof ts);
+    constructor(caseSensitive: boolean, typescript: typeof ts);
     addGulp(gFile: VinylFile): File;
     addContent(fileName: string, content: string): File;
     private addFile;
@@ -50,10 +51,12 @@ export declare class FileCache {
     previous: FileDictionary;
     current: FileDictionary;
     options: ts.CompilerOptions;
+    caseSensitive: boolean;
     noParse: boolean;
     typescript: typeof ts;
     version: number;
-    constructor(typescript: typeof ts, options: ts.CompilerOptions);
+    versionString: string;
+    constructor(typescript: typeof ts, options: ts.CompilerOptions, caseSensitive: boolean);
     addGulp(gFile: VinylFile): File;
     addContent(fileName: string, content: string): File;
     reset(): void;
diff --git a/release/input.js b/release/input.js
index 09abebec..c8c6ca90 100644
--- a/release/input.js
+++ b/release/input.js
@@ -17,21 +17,21 @@ var FileKind;
 })(FileKind = exports.FileKind || (exports.FileKind = {}));
 var File;
 (function (File) {
-    function fromContent(fileName, content) {
+    function fromContent(caseSensitive, fileName, content) {
         let kind = FileKind.Source;
         if (path.extname(fileName).toLowerCase() === 'json')
             kind = FileKind.Config;
         return {
-            fileNameNormalized: utils.normalizePath(fileName),
+            fileNameNormalized: utils.normalizePath(caseSensitive, fileName),
             fileNameOriginal: fileName,
             content,
             kind
         };
     }
     File.fromContent = fromContent;
-    function fromGulp(file) {
+    function fromGulp(caseSensitive, file) {
         let str = file.contents.toString('utf8');
-        let data = fromContent(file.path, str);
+        let data = fromContent(caseSensitive, file.path, str);
         data.gulp = file;
         return data;
     }
@@ -58,16 +58,17 @@ var File;
     File.getChangeState = getChangeState;
 })(File = exports.File || (exports.File = {}));
 class FileDictionary {
-    constructor(typescript) {
+    constructor(caseSensitive, typescript) {
         this.files = {};
         this.firstSourceFile = undefined;
+        this.caseSensitive = caseSensitive;
         this.typescript = typescript;
     }
     addGulp(gFile) {
-        return this.addFile(File.fromGulp(gFile));
+        return this.addFile(File.fromGulp(this.caseSensitive, gFile));
     }
     addContent(fileName, content) {
-        return this.addFile(File.fromContent(fileName, content));
+        return this.addFile(File.fromContent(this.caseSensitive, fileName, content));
     }
     addFile(file) {
         if (file.kind === FileKind.Source) {
@@ -79,7 +80,7 @@ class FileDictionary {
         return file;
     }
     getFile(name) {
-        return this.files[utils.normalizePath(name)];
+        return this.files[utils.normalizePath(this.caseSensitive, name)];
     }
     getFileNames(onlyGulp = false) {
         const fileNames = [];
@@ -107,7 +108,7 @@ class FileDictionary {
     get commonBasePath() {
         const fileNames = this.getSourceFileNames(true);
         return utils.getCommonBasePathOfArray(fileNames.map(fileName => {
-            const file = this.files[utils.normalizePath(fileName)];
+            const file = this.files[utils.normalizePath(this.caseSensitive, fileName)];
             return path.resolve(process.cwd(), file.gulp.base);
         }));
     }
@@ -117,7 +118,7 @@ class FileDictionary {
     get commonSourceDirectory() {
         const fileNames = this.getSourceFileNames();
         return utils.getCommonBasePathOfArray(fileNames.map(fileName => {
-            const file = this.files[utils.normalizePath(fileName)];
+            const file = this.files[utils.normalizePath(this.caseSensitive, fileName)];
             return path.dirname(file.fileNameNormalized);
         }));
     }
@@ -127,12 +128,14 @@ class FileDictionary {
 }
 exports.FileDictionary = FileDictionary;
 class FileCache {
-    constructor(typescript, options) {
+    constructor(typescript, options, caseSensitive) {
         this.previous = undefined;
         this.noParse = false; // true when using a file based compiler.
         this.version = 0;
+        this.versionString = "0";
         this.typescript = typescript;
         this.options = options;
+        this.caseSensitive = caseSensitive;
         this.createDictionary();
     }
     addGulp(gFile) {
@@ -143,11 +146,12 @@ class FileCache {
     }
     reset() {
         this.version++;
+        this.versionString = this.version.toString();
         this.previous = this.current;
         this.createDictionary();
     }
     createDictionary() {
-        this.current = new FileDictionary(this.typescript);
+        this.current = new FileDictionary(this.caseSensitive, this.typescript);
         this.current.initTypeScriptSourceFile = (file) => this.initTypeScriptSourceFile(file);
     }
     initTypeScriptSourceFile(file) {
@@ -161,6 +165,7 @@ class FileCache {
             }
         }
         file.ts = this.typescript.createSourceFile(file.fileNameOriginal, file.content, this.options.target);
+        file.ts.version = this.versionString;
     }
     getFile(name) {
         return this.current.getFile(name);
diff --git a/release/main.js b/release/main.js
index 38224361..da1575f8 100644
--- a/release/main.js
+++ b/release/main.js
@@ -4,8 +4,10 @@ var __rest = (this && this.__rest) || function (s, e) {
     for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)
         t[p] = s[p];
     if (s != null && typeof Object.getOwnPropertySymbols === "function")
-        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) if (e.indexOf(p[i]) < 0)
-            t[p[i]] = s[p[i]];
+        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) {
+            if (e.indexOf(p[i]) < 0 && Object.prototype.propertyIsEnumerable.call(s, p[i]))
+                t[p[i]] = s[p[i]];
+        }
     return t;
 };
 const path = require("path");
diff --git a/release/output.js b/release/output.js
index 3b9a0075..13daff59 100644
--- a/release/output.js
+++ b/release/output.js
@@ -1,9 +1,10 @@
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/release/project.js b/release/project.js
index 3d9b855c..9663d11c 100644
--- a/release/project.js
+++ b/release/project.js
@@ -4,8 +4,10 @@ var __rest = (this && this.__rest) || function (s, e) {
     for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)
         t[p] = s[p];
     if (s != null && typeof Object.getOwnPropertySymbols === "function")
-        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) if (e.indexOf(p[i]) < 0)
-            t[p[i]] = s[p[i]];
+        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) {
+            if (e.indexOf(p[i]) < 0 && Object.prototype.propertyIsEnumerable.call(s, p[i]))
+                t[p[i]] = s[p[i]];
+        }
     return t;
 };
 Object.defineProperty(exports, "__esModule", { value: true });
@@ -19,7 +21,8 @@ const input_1 = require("./input");
 const output_1 = require("./output");
 const compiler_1 = require("./compiler");
 function setupProject(projectDirectory, configFileName, rawConfig, config, options, projectReferences, typescript, finalTransformers) {
-    const input = new input_1.FileCache(typescript, options);
+    const caseSensitive = typescript.createCompilerHost(options).useCaseSensitiveFileNames();
+    const input = new input_1.FileCache(typescript, options, caseSensitive);
     const compiler = options.isolatedModules ? new compiler_1.FileCompiler() : new compiler_1.ProjectCompiler();
     let running = false;
     if (options.isolatedModules) {
diff --git a/release/utils.d.ts b/release/utils.d.ts
index 263b102d..d9382d0a 100644
--- a/release/utils.d.ts
+++ b/release/utils.d.ts
@@ -5,7 +5,7 @@ export interface Map<T> {
     [key: string]: T;
 }
 export declare function forwardSlashes(fileName: string): string;
-export declare function normalizePath(pathString: string): string;
+export declare function normalizePath(caseSensitive: boolean, pathString: string): string;
 /**
  * Splits a filename into an extensionless filename and an extension.
  * 'bar/foo.js' is turned into ['bar/foo', 'js']
diff --git a/release/utils.js b/release/utils.js
index 488e76bf..38ce6c78 100644
--- a/release/utils.js
+++ b/release/utils.js
@@ -6,8 +6,11 @@ function forwardSlashes(fileName) {
     return fileName.replace(/\\/g, '/');
 }
 exports.forwardSlashes = forwardSlashes;
-function normalizePath(pathString) {
-    return path.normalize(pathString).toLowerCase();
+function normalizePath(caseSensitive, pathString) {
+    const normalized = path.normalize(pathString);
+    if (!caseSensitive)
+        return normalized.toLowerCase();
+    return normalized;
 }
 exports.normalizePath = normalizePath;
 /**
diff --git a/test/baselines/emitDeclarationOnly/2.9/dts/a.d.ts b/test/baselines/emitDeclarationOnly/3.6/dts/a.d.ts
similarity index 62%
rename from test/baselines/emitDeclarationOnly/2.9/dts/a.d.ts
rename to test/baselines/emitDeclarationOnly/3.6/dts/a.d.ts
index 17681864..b3a0b19d 100644
--- a/test/baselines/emitDeclarationOnly/2.9/dts/a.d.ts
+++ b/test/baselines/emitDeclarationOnly/3.6/dts/a.d.ts
@@ -1,3 +1,3 @@
 export declare class Hello {
-  value: string;
+    value: string;
 }
diff --git a/test/baselines/emitDeclarationOnly/2.9/errors.txt b/test/baselines/emitDeclarationOnly/3.6/errors.txt
similarity index 100%
rename from test/baselines/emitDeclarationOnly/2.9/errors.txt
rename to test/baselines/emitDeclarationOnly/3.6/errors.txt