diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
index 0bba375a2cb..7d2f61b6d6f 100644
--- a/src/compiler/declarationEmitter.ts
+++ b/src/compiler/declarationEmitter.ts
@@ -416,7 +416,9 @@ namespace ts {
                 case SyntaxKind.TypeOperator:
                     return emitTypeOperator(<TypeOperatorNode>type);
                 case SyntaxKind.IndexedAccessType:
-                    return emitPropertyAccessType(<IndexedAccessTypeNode>type);
+                    return emitIndexedAccessType(<IndexedAccessTypeNode>type);
+                case SyntaxKind.MappedType:
+                    return emitMappedType(<MappedTypeNode>type);
                 case SyntaxKind.FunctionType:
                 case SyntaxKind.ConstructorType:
                     return emitSignatureDeclarationWithJsDocComments(<FunctionOrConstructorTypeNode>type);
@@ -516,13 +518,39 @@ namespace ts {
                 emitType(type.type);
             }
 
-            function emitPropertyAccessType(node: IndexedAccessTypeNode) {
+            function emitIndexedAccessType(node: IndexedAccessTypeNode) {
                 emitType(node.objectType);
                 write("[");
                 emitType(node.indexType);
                 write("]");
             }
 
+            function emitMappedType(node: MappedTypeNode) {
+                const prevEnclosingDeclaration = enclosingDeclaration;
+                enclosingDeclaration = node;
+                write("{");
+                writeLine();
+                increaseIndent();
+                if (node.readonlyToken) {
+                    write("readonly ");
+                }
+                write("[");
+                writeEntityName(node.typeParameter.name);
+                write(" in ");
+                emitType(node.typeParameter.constraint);
+                write("]");
+                if (node.questionToken) {
+                    write("?");
+                }
+                write(": ");
+                emitType(node.type);
+                write(";");
+                writeLine();
+                decreaseIndent();
+                write("}");
+                enclosingDeclaration = prevEnclosingDeclaration;
+            }
+
             function emitTypeLiteral(type: TypeLiteralNode) {
                 write("{");
                 if (type.members.length) {
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index fa0d44a695f..a18146bdaa1 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -606,7 +606,9 @@ const _super = (function (geti, seti) {
                 case SyntaxKind.TypeOperator:
                     return emitTypeOperator(<TypeOperatorNode>node);
                 case SyntaxKind.IndexedAccessType:
-                    return emitPropertyAccessType(<IndexedAccessTypeNode>node);
+                    return emitIndexedAccessType(<IndexedAccessTypeNode>node);
+                case SyntaxKind.MappedType:
+                    return emitMappedType(<MappedTypeNode>node);
                 case SyntaxKind.LiteralType:
                     return emitLiteralType(<LiteralTypeNode>node);
 
@@ -1109,13 +1111,36 @@ const _super = (function (geti, seti) {
             emit(node.type);
         }
 
-        function emitPropertyAccessType(node: IndexedAccessTypeNode) {
+        function emitIndexedAccessType(node: IndexedAccessTypeNode) {
             emit(node.objectType);
             write("[");
             emit(node.indexType);
             write("]");
         }
 
+        function emitMappedType(node: MappedTypeNode) {
+            write("{");
+            writeLine();
+            increaseIndent();
+            if (node.readonlyToken) {
+                write("readonly ");
+            }
+            write("[");
+            emit(node.typeParameter.name);
+            write(" in ");
+            emit(node.typeParameter.constraint);
+            write("]");
+            if (node.questionToken) {
+                write("?");
+            }
+            write(": ");
+            emit(node.type);
+            write(";");
+            writeLine();
+            decreaseIndent();
+            write("}");
+        }
+
         function emitLiteralType(node: LiteralTypeNode) {
             emitExpression(node.literal);
         }