diff --git a/src/gtk/app.cpp b/src/gtk/app.cpp
index 866a4faab8..c3f805327c 100644
--- a/src/gtk/app.cpp
+++ b/src/gtk/app.cpp
@@ -13,6 +13,7 @@
 
 #ifdef __VMS
 #include <vms_jackets.h>
+#undef ConnectionNumber
 #endif
 
 #include "wx/app.h"
diff --git a/src/gtk1/app.cpp b/src/gtk1/app.cpp
index 866a4faab8..c3f805327c 100644
--- a/src/gtk1/app.cpp
+++ b/src/gtk1/app.cpp
@@ -13,6 +13,7 @@
 
 #ifdef __VMS
 #include <vms_jackets.h>
+#undef ConnectionNumber
 #endif
 
 #include "wx/app.h"