diff --git a/src/proto/misc2.pro b/src/proto/misc2.pro
index 770bd33..b821417 100644
--- a/src/proto/misc2.pro
+++ b/src/proto/misc2.pro
@@ -21,6 +21,7 @@
 int leftcol_changed(void);
 void vim_mem_profile_dump(void);
 char_u *alloc(unsigned size);
+int alloc_does_fail(long_u size);
 char_u *alloc_id(unsigned size, alloc_id_T id);
 char_u *alloc_clear(unsigned size);
 char_u *alloc_check(unsigned size);