diff --git a/dtool/src/dtoolutil/filename_assist.mm b/dtool/src/dtoolutil/filename_assist.mm
index 7e93893de6..a09cfa6704 100644
--- a/dtool/src/dtoolutil/filename_assist.mm
+++ b/dtool/src/dtoolutil/filename_assist.mm
@@ -16,6 +16,7 @@
 
 #ifdef IS_OSX
 
+#include <strings.h>
 #include <Foundation/Foundation.h>
 
 #ifndef BUILD_IPHONE