diff --git a/tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts b/tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts
index a8a580150e8..2e54b335537 100644
--- a/tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts
+++ b/tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts
@@ -1,3 +1,5 @@
+// @noImplicitAny: true
+
 let cond: boolean;
 
 function len(s: string) {
@@ -46,3 +48,46 @@ function g2() {
     }
     x;
 }
+
+function asNumber(x: string | number): number {
+    return +x;
+}
+
+function h1() {
+    let x: string | number | boolean;
+    x = "0";
+    while (cond) {
+        x = +x + 1;
+        x;
+    }
+}
+
+function h2() {
+    let x: string | number | boolean;
+    x = "0";
+    while (cond) {
+        x = asNumber(x) + 1;
+        x;
+    }
+}
+
+function h3() {
+    let x: string | number | boolean;
+    x = "0";
+    while (cond) {
+        let y = asNumber(x);
+        x = y + 1;
+        x;
+    }
+}
+
+function h4() {
+    let x: string | number | boolean;
+    x = "0";
+    while (cond) {
+        x;
+        let y = asNumber(x);
+        x = y + 1;
+        x;
+    }
+}