diff --git a/dlls/comctl32/commctrl.c b/dlls/comctl32/commctrl.c
index 45b93bdc8b5..c228b647f87 100644
--- a/dlls/comctl32/commctrl.c
+++ b/dlls/comctl32/commctrl.c
@@ -1082,6 +1082,9 @@ BOOL WINAPI SetWindowSubclass (HWND hWnd, SUBCLASSPROC pfnSubclass,
 
    TRACE ("(%p, %p, %lx, %lx)\n", hWnd, pfnSubclass, uIDSubclass, dwRef);
 
+   if (!hWnd || !pfnSubclass)
+       return FALSE;
+
    /* Since the window procedure that we set here has two additional arguments,
     * we can't simply set it as the new window procedure of the window. So we
     * set our own window procedure and then calculate the other two arguments
diff --git a/dlls/comctl32/tests/subclass.c b/dlls/comctl32/tests/subclass.c
index 75a134352ec..41ba06560ac 100644
--- a/dlls/comctl32/tests/subclass.c
+++ b/dlls/comctl32/tests/subclass.c
@@ -218,46 +218,61 @@ static LRESULT WINAPI wnd_proc_sub(HWND hwnd, UINT message, WPARAM wParam, LPARA
 
 static void test_subclass(void)
 {
+    BOOL ret;
     HWND hwnd = CreateWindowExA(0, "TestSubclass", "Test subclass", WS_OVERLAPPEDWINDOW,
                            100, 100, 200, 200, 0, 0, 0, NULL);
     ok(hwnd != NULL, "failed to create test subclass wnd\n");
 
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 2, 0);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 2, 0);
+    ok(ret == TRUE, "Expected TRUE\n");
     SendMessageA(hwnd, WM_USER, 1, 0);
     SendMessageA(hwnd, WM_USER, 2, 0);
     ok_sequence(Sub_BasicTest, "Basic");
 
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 2, DELETE_SELF);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 2, DELETE_SELF);
+    ok(ret == TRUE, "Expected TRUE\n");
     SendMessageA(hwnd, WM_USER, 1, 1);
     ok_sequence(Sub_DeletedTest, "Deleted");
 
     SendMessageA(hwnd, WM_USER, 1, 0);
     ok_sequence(Sub_AfterDeletedTest, "After Deleted");
 
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 2, 0);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 2, 0);
+    ok(ret == TRUE, "Expected TRUE\n");
     orig_proc_3 = (WNDPROC)SetWindowLongPtrA(hwnd, GWLP_WNDPROC, (LONG_PTR)wnd_proc_3);
     SendMessageA(hwnd, WM_USER, 1, 0);
     SendMessageA(hwnd, WM_USER, 2, 0);
     ok_sequence(Sub_OldAfterNewTest, "Old after New");
 
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 4, 0);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 4, 0);
+    ok(ret == TRUE, "Expected TRUE\n");
     SendMessageA(hwnd, WM_USER, 1, 0);
     ok_sequence(Sub_MixTest, "Mix");
 
     /* Now the fun starts */
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 4, SEND_NEST);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 4, SEND_NEST);
+    ok(ret == TRUE, "Expected TRUE\n");
     SendMessageA(hwnd, WM_USER, 1, 1);
     ok_sequence(Sub_MixAndNestTest, "Mix and nest");
 
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 4, SEND_NEST | DELETE_SELF);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 4, SEND_NEST | DELETE_SELF);
+    ok(ret == TRUE, "Expected TRUE\n");
     SendMessageA(hwnd, WM_USER, 1, 1);
     ok_sequence(Sub_MixNestDelTest, "Mix, nest, del");
 
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 4, 0);
-    pSetWindowSubclass(hwnd, wnd_proc_sub, 5, DELETE_PREV);
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 4, 0);
+    ok(ret == TRUE, "Expected TRUE\n");
+    ret = pSetWindowSubclass(hwnd, wnd_proc_sub, 5, DELETE_PREV);
+    ok(ret == TRUE, "Expected TRUE\n");
     SendMessageA(hwnd, WM_USER, 1, 1);
     ok_sequence(Sub_MixDelPrevTest, "Mix and del prev");
 
+    ret = pSetWindowSubclass(NULL, wnd_proc_sub, 1, 0);
+    ok(ret == FALSE, "Expected FALSE\n");
+
+    ret = pSetWindowSubclass(hwnd, NULL, 1, 0);
+    ok(ret == FALSE, "Expected FALSE\n");
+
     DestroyWindow(hwnd);
 }