diff --git a/src/proto/os_unix.pro b/src/proto/os_unix.pro
index 721c07d..0117b1e 100644
--- a/src/proto/os_unix.pro
+++ b/src/proto/os_unix.pro
@@ -72,6 +72,7 @@
 int mch_has_exp_wildcard(char_u *p);
 int mch_has_wildcard(char_u *p);
 int mch_rename(const char *src, const char *dest);
+int gpm_enabled(void);
 int mch_libcall(char_u *libname, char_u *funcname, char_u *argstring, int argint, char_u **string_result, int *number_result);
 void setup_term_clip(void);
 void start_xterm_trace(int button);