diff --git a/src/mod/endpoints/mod_gsmopen/libctb-0.16/include/ctb-0.16/serportx.h b/src/mod/endpoints/mod_gsmopen/libctb-0.16/include/ctb-0.16/serportx.h
index bb00d97672..4d29bb4ccc 100644
--- a/src/mod/endpoints/mod_gsmopen/libctb-0.16/include/ctb-0.16/serportx.h
+++ b/src/mod/endpoints/mod_gsmopen/libctb-0.16/include/ctb-0.16/serportx.h
@@ -13,7 +13,7 @@
 #include <string.h>
 #include "ctb-0.16/iobase.h"
 
-#if _MSC_VER < 1900
+#if defined(_MSC_VER) && _MSC_VER < 1900
 # define snprintf _snprintf
 #endif