diff --git a/src/runtime/gc_test.go b/src/runtime/gc_test.go
index 1ea1c2c745a..273f399864b 100644
--- a/src/runtime/gc_test.go
+++ b/src/runtime/gc_test.go
@@ -205,15 +205,24 @@ func TestGcZombieReporting(t *testing.T) {
 func TestGCTestMoveStackOnNextCall(t *testing.T) {
 	t.Parallel()
 	var onStack int
-	runtime.GCTestMoveStackOnNextCall()
-	moveStackCheck(t, &onStack, uintptr(unsafe.Pointer(&onStack)))
+	// GCTestMoveStackOnNextCall can fail in rare cases if there's
+	// a preemption. This won't happen many times in quick
+	// succession, so just retry a few times.
+	for retry := 0; retry < 5; retry++ {
+		runtime.GCTestMoveStackOnNextCall()
+		if moveStackCheck(t, &onStack, uintptr(unsafe.Pointer(&onStack))) {
+			// Passed.
+			return
+		}
+	}
+	t.Fatal("stack did not move")
 }
 
 // This must not be inlined because the point is to force a stack
 // growth check and move the stack.
 //
 //go:noinline
-func moveStackCheck(t *testing.T, new *int, old uintptr) {
+func moveStackCheck(t *testing.T, new *int, old uintptr) bool {
 	// new should have been updated by the stack move;
 	// old should not have.
 
@@ -228,8 +237,9 @@ func moveStackCheck(t *testing.T, new *int, old uintptr) {
 			t.Fatalf("test bug: new (%#x) should be a stack pointer, not %s", new2, cls)
 		}
 		// This was a real failure.
-		t.Fatal("stack did not move")
+		return false
 	}
+	return true
 }
 
 func TestGCTestIsReachable(t *testing.T) {
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index ecac354d833..f0c03b51028 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -2347,6 +2347,9 @@ func fmtNSAsMS(buf []byte, ns uint64) []byte {
 // if any other work appears after this call (such as returning).
 // Typically the following call should be marked go:noinline so it
 // performs a stack check.
+//
+// In rare cases this may not cause the stack to move, specifically if
+// there's a preemption between this call and the next.
 func gcTestMoveStackOnNextCall() {
 	gp := getg()
 	gp.stackguard0 = getcallersp()