diff --git a/src/window.cc b/src/window.cc
index 3357852..f9beff1 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -1725,7 +1725,7 @@ bool _windowAddButtonGfx(const char* buttonName, char* pressedFileName, char* no
 // 0x4BA11C
 bool _windowAddButtonProc(const char* buttonName, Program* program, int mouseEnterProc, int mouseExitProc, int mouseDownProc, int mouseUpProc)
 {
-    if (gCurrentManagedWindowIndex != -1) {
+    if (gCurrentManagedWindowIndex == -1) {
         return false;
     }