diff --git a/libsrc/geos-common/dlgbox/messagebox.c b/libsrc/geos-common/dlgbox/messagebox.c
index fd4a5cd11..141a84b89 100644
--- a/libsrc/geos-common/dlgbox/messagebox.c
+++ b/libsrc/geos-common/dlgbox/messagebox.c
@@ -7,6 +7,7 @@
 
 #include <geos.h>
 #include <stdio.h>
+#include <stdarg.h>
 
 void _mbprintout(void);