System classes must not have the CS_GLOBALCLASS style.

controls/listbox.c

diff --git a/controls/listbox.c b/controls/listbox.c
index 3f807e3..d72ecc3 100644
--- a/controls/listbox.c
+++ b/controls/listbox.c
@@ -139,7 +139,7 @@
 const struct builtin_class_descr LISTBOX_builtin_class =
 {
     "ListBox",            /* name */
-    CS_GLOBALCLASS | CS_DBLCLKS /*| CS_PARENTDC*/,  /* style */
+    CS_DBLCLKS /*| CS_PARENTDC*/,  /* style */
     ListBoxWndProcA,      /* procA */
     ListBoxWndProcW,      /* procW */
     sizeof(LB_DESCR *),   /* extra */
@@ -154,7 +154,7 @@
 const struct builtin_class_descr COMBOLBOX_builtin_class =
 {
     "ComboLBox",          /* name */
-    CS_GLOBALCLASS | CS_DBLCLKS | CS_SAVEBITS,  /* style */
+    CS_DBLCLKS | CS_SAVEBITS,  /* style */
     ComboLBWndProcA,      /* procA */
     ComboLBWndProcW,      /* procW */
     sizeof(LB_DESCR *),   /* extra */