diff --git a/tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck62.ts b/tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck62.ts
new file mode 100644
index 00000000000..2f30fe9d902
--- /dev/null
+++ b/tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck62.ts
@@ -0,0 +1,40 @@
+// @module: commonjs
+// @target: es6
+// @noImplicitAny: true
+
+export interface StrategicState {
+    lastStrategyApplied?: string;
+}
+
+export function strategy<T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T | undefined>): (a: T) => IterableIterator<T | undefined> {
+    return function*(state) {
+        for (const next of gen(state)) {
+            if (next) {
+                next.lastStrategyApplied = stratName;
+            }
+            yield next;
+        }
+    }
+}
+
+export interface Strategy<T> {
+    (a: T): IterableIterator<T | undefined>;
+}
+
+export interface State extends StrategicState {
+    foo: number;
+}
+
+export const Nothing1: Strategy<State> = strategy("Nothing", function*(state: State) {
+    return state;
+});
+
+export const Nothing2: Strategy<State> = strategy("Nothing", function*(state: State) {
+    yield state;
+});
+
+export const Nothing3: Strategy<State> = strategy("Nothing", function* (state: State) {
+    yield ;
+    return state;
+});
+ 
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts b/tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts
new file mode 100644
index 00000000000..58411e409b8
--- /dev/null
+++ b/tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts
@@ -0,0 +1,43 @@
+// @module: commonjs
+// @target: es6
+// @noImplicitAny: true
+
+export interface StrategicState {
+    lastStrategyApplied?: string;
+}
+
+export function strategy<T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T | undefined>): (a: T) => IterableIterator<T | undefined> {
+    return function*(state) {
+        for (const next of gen(state)) {
+            if (next) {
+                next.lastStrategyApplied = stratName;
+            }
+            yield next;
+        }
+    }
+}
+
+export interface Strategy<T> {
+    (a: T): IterableIterator<T | undefined>;
+}
+
+export interface State extends StrategicState {
+    foo: number;
+}
+
+export const Nothing: Strategy<State> = strategy("Nothing", function* (state: State) {
+    yield 1;
+    return state;
+});
+
+export const Nothing1: Strategy<State> = strategy("Nothing", function* (state: State) {
+});
+
+export const Nothing2: Strategy<State> = strategy("Nothing", function* (state: State) {
+    return 1;
+});
+
+export const Nothing3: Strategy<State> = strategy("Nothing", function* (state: State) {
+    yield state;
+    return 1;
+});
\ No newline at end of file