diff --git a/src/main/cup/parser.cup b/src/main/cup/parser.cup
index 24eff22..b64e3b1 100644
--- a/src/main/cup/parser.cup
+++ b/src/main/cup/parser.cup
@@ -53,5 +53,6 @@ term ::=
 
 factor ::=
   LITNUM:x               {: RESULT = new ExpNum(x);     :}
+| MINUS factor:x         {: RESULT = new ExpNegate(x);  :}
 | LPAREN exp:x RPAREN    {: RESULT = x;     :}
 ;
diff --git a/src/main/java/absyn/ExpNegate.java b/src/main/java/absyn/ExpNegate.java
new file mode 100644
index 0000000..fa79998
--- /dev/null
+++ b/src/main/java/absyn/ExpNegate.java
@@ -0,0 +1,28 @@
+package absyn;
+
+import javaslang.collection.Tree;
+import static org.bytedeco.javacpp.LLVM.*;
+
+/**
+ * Created by mvosouza on 19.10.16.
+ */
+public class ExpNegate extends Exp{
+
+    public final Exp arg;
+
+    public ExpNegate(Exp arg) {
+        this.arg = arg;
+    }
+
+    @Override
+    public LLVMValueRef codegen(LLVMModuleRef module, LLVMBuilderRef builder) {
+        final LLVMValueRef v_arg = arg.codegen(module,builder);
+        final LLVMValueRef zero = LLVMConstReal(LLVMDoubleType(), 0);
+        return LLVMBuildFSub(builder, zero, v_arg, "subtmp");
+    }
+
+    @Override
+    public Tree.Node<String> toTree() {
+        return Tree.of("ExpNegate", arg.toTree());
+    }
+}