diff --git a/common/controls.c b/common/controls.c
index b9e0d7ab..473ba7a3 100644
--- a/common/controls.c
+++ b/common/controls.c
@@ -237,6 +237,10 @@ void uiControlSetParent(uiControl *c, uiControl *parent)
 		uiprivProgrammerErrorReparenting("a", "another", uiprivFunc);
 		return;
 	}
+	if (parentHasCycle(c, parent)) {
+		uiprivProgrammerErrorControlParentCycle(uiprivFunc);
+		return;
+	}
 	c->parent = parent;
 }
 
diff --git a/common/programmererrors.h b/common/programmererrors.h
index 038422be..26f9597b 100644
--- a/common/programmererrors.h
+++ b/common/programmererrors.h
@@ -75,4 +75,7 @@
 	uiprivProgrammerError("%s(): cannot set a control with %s parent to have %s parent", \
 		func, current, next)
 
+#define uiprivProgrammerErrorControlParentCycle(func) \
+	uiprivProgrammerError("%s(): cannot create a parent cycle", func)
+
 // }
diff --git a/test/controls.c b/test/controls.c
index c2b06d58..262c48be 100644
--- a/test/controls.c
+++ b/test/controls.c
@@ -435,7 +435,7 @@ Test(ControlParentCyclesDisallowed_TwoControls)
 	d = uiNewControl(testControlType(), NULL);
 
 	uiControlSetParent(c, d);
-	ctx = beginCheckProgrammerError("TODO");
+	ctx = beginCheckProgrammerError("uiControlSetParent(): cannot create a parent cycle");
 	uiControlSetParent(d, c);
 	endCheckProgrammerError(ctx);
 
@@ -457,7 +457,7 @@ Test(ControlParentCyclesDisallowed_ThreeControls)
 
 	uiControlSetParent(c, d);
 	uiControlSetParent(d, e);
-	ctx = beginCheckProgrammerError("TODO");
+	ctx = beginCheckProgrammerError("uiControlSetParent(): cannot create a parent cycle");
 	uiControlSetParent(e, c);
 	endCheckProgrammerError(ctx);
 
@@ -475,7 +475,7 @@ Test(ControlCannotBeItsOwnParent)
 	void *ctx;
 
 	c = uiNewControl(testControlType(), NULL);
-	ctx = beginCheckProgrammerError("TODO");
+	ctx = beginCheckProgrammerError("uiControlSetParent(): cannot create a parent cycle");
 	uiControlSetParent(c, c);
 	endCheckProgrammerError(ctx);
 	uiControlFree(c);