diff --git a/lib/dashdash.js b/lib/dashdash.js
index adb6f13..1368a9c 100644
--- a/lib/dashdash.js
+++ b/lib/dashdash.js
@@ -103,7 +103,33 @@ function optionKeyFromName(name) {
     return name.replace(/-/g, '_');
 }
 
-
+// ---- Error types
+var error_names = [
+    "NOT_A_NUMBER",
+    "NOT_AN_INTEGER",
+    "NOT_A_POSITIVE_INTEGER",
+    "NOT_A_DATE_FORMAT",
+    "INVALID_DATE",
+    "UNKNOWN_OPTION",
+    "UNKNOWN_OPTION_IN_GROUP",
+    "ARG_TO_OPTION_NOT_ALLOWED",
+    "ARG_TO_OPTION_MISSING"
+]
+
+var ERRORS = {};
+error_names.forEach(function(n) {
+    ERRORS[n] = n;
+})
+
+function augment_error(err, type, data) {
+    err.type = type;
+    if (data) {
+	Object.keys(data).forEach(function (k) {
+	    err[k] = data[k];
+	})
+    }
+    return err;
+}
 
 // ---- Option types
 
@@ -120,8 +146,12 @@ function parseNumber(option, optstr, arg) {
     assert.string(arg, 'arg');
     var num = Number(arg);
     if (isNaN(num)) {
-        throw new Error(format('arg for "%s" is not a number: "%s"',
-            optstr, arg));
+        throw augment_error(
+	    new Error(format('arg for "%s" is not a number: "%s"',
+                optstr, arg)),
+	    ERRORS.NOT_A_NUMBER,
+	    {optstr: optstr, arg: arg}
+	)
     }
     return num;
 }
@@ -130,8 +160,12 @@ function parseInteger(option, optstr, arg) {
     assert.string(arg, 'arg');
     var num = Number(arg);
     if (!/^[0-9-]+$/.test(arg) || isNaN(num)) {
-        throw new Error(format('arg for "%s" is not an integer: "%s"',
-            optstr, arg));
+        throw augment_error(
+	    new Error(format('arg for "%s" is not an integer: "%s"',
+                optstr, arg)),
+	    ERRORS.NOT_AN_INTEGER,
+	    {optstr: optstr, arg: arg}
+	)
     }
     return num;
 }
@@ -140,8 +174,12 @@ function parsePositiveInteger(option, optstr, arg) {
     assert.string(arg, 'arg');
     var num = Number(arg);
     if (!/^[0-9]+$/.test(arg) || isNaN(num) || num === 0) {
-        throw new Error(format('arg for "%s" is not a positive integer: "%s"',
-            optstr, arg));
+        throw augment_error(
+	    new Error(format('arg for "%s" is not a positive integer: "%s"',
+                optstr, arg)),
+	    ERRORS.NOT_A_POSITIVE_INTEGER,
+	    {optstr: optstr, arg: arg}
+	)
     }
     return num;
 }
@@ -167,12 +205,20 @@ function parseDate(option, optstr, arg) {
         // ISO 8601 format
         date = new Date(arg);
     } else {
-        throw new Error(format('arg for "%s" is not a valid date format: "%s"',
-            optstr, arg));
+        throw augment_error(
+	    new Error(format('arg for "%s" is not a valid date format: "%s"',
+                optstr, arg)),
+	    ERRORS.NOT_A_DATE_FORMAT,
+	    {optstr: optstr, arg: arg}
+	)
     }
     if (date.toString() === 'Invalid Date') {
-        throw new Error(format('arg for "%s" is an invalid date: "%s"',
-            optstr, arg));
+        throw augment_error(
+	    new Error(format('arg for "%s" is an invalid date: "%s"',
+                optstr, arg)),
+	    ERRORS.INVALID_DATE,
+	    {optstr: optstr, arg: arg}
+	)
     }
     return date;
 }
@@ -417,7 +463,11 @@ Parser.prototype.parse = function parse(inputs) {
             var option = this.optionFromName[name];
             if (!option) {
                 if (!this.allowUnknown)
-                    throw new Error(format('unknown option: "--%s"', name));
+		    throw augment_error(
+			new Error(format('unknown option: "--%s"', name)),
+			ERRORS.UNKNOWN_OPTION,
+			{optstr: format("--%s", name)}
+		    )
                 else if (this.interspersed)
                     _args.push(arg);
                 else
@@ -425,16 +475,24 @@ Parser.prototype.parse = function parse(inputs) {
             } else {
                 var takesArg = this.optionTakesArg(option);
                 if (val !== null && !takesArg) {
-                    throw new Error(format('argument given to "--%s" option '
-                        + 'that does not take one: "%s"', name, arg));
+		    throw augment_error(
+			new Error(format('argument given to "--%s" option '
+                            + 'that does not take one: "%s"', name, arg)),
+			ERRORS.ARG_TO_OPTION_NOT_ALLOWED,
+			{optstr: format("--%s", name), arg: arg}
+		    )
                 }
                 if (!takesArg) {
                     addOpt(option, '--'+name, option.key, true, 'argv');
                 } else if (val !== null) {
                     addOpt(option, '--'+name, option.key, val, 'argv');
                 } else if (i + 1 >= args.length) {
-                    throw new Error(format('do not have enough args for "--%s" '
-                        + 'option', name));
+		    throw augment_error(
+			new Error(format('do not have enough args for "--%s" '
+                            + 'option', name)),
+			ERRORS.ARG_TO_OPTION_MISSING,
+			{optstr: format("--%s", name)}
+		    )
                 } else {
                     addOpt(option, '--'+name, option.key, args[i + 1], 'argv');
                     i++;
@@ -457,11 +515,19 @@ Parser.prototype.parse = function parse(inputs) {
                         } else
                             break outer;
                     } else if (arg.length > 2) {
-                        throw new Error(format(
-                            'unknown option: "-%s" in "%s" group',
-                            name, arg));
+			throw augment_error(
+			    new Error(format(
+				'unknown option: "-%s" in "%s" group',
+				name, arg)),
+			    ERRORS.UNKNOWN_OPTION_IN_GROUP,
+			    {optstr: format("-%s", name), group: arg}
+			)
                     } else {
-                        throw new Error(format('unknown option: "-%s"', name));
+			throw augment_error(
+			    new Error(format('unknown option: "-%s"', name)),
+			    ERRORS.UNKNOWN_OPTION,
+			    {optstr: format("-%s", name)}
+			)
                     }
                 } else if (this.optionTakesArg(option)) {
                     break;
@@ -482,8 +548,12 @@ Parser.prototype.parse = function parse(inputs) {
                     break;
                 } else {
                     if (i + 1 >= args.length) {
-                        throw new Error(format('do not have enough args '
-                            + 'for "-%s" option', name));
+			throw augment_error(
+			    new Error(format('do not have enough args '
+                                + 'for "-%s" option', name)),
+			    ERRORS.ARG_TO_OPTION_MISSING,
+			    {optstr: format("-%s", name)}
+			)
                     }
                     addOpt(option, '-'+name, option.key, args[i + 1], 'argv');
                     i++;
@@ -1051,5 +1121,9 @@ module.exports = {
     parseNumber: parseNumber,
     parseInteger: parseInteger,
     parsePositiveInteger: parsePositiveInteger,
-    parseDate: parseDate
+    parseDate: parseDate,
+
+    // Export the error types
+  ERRORS: ERRORS,
+  augment_error: augment_error
 };