diff --git a/src/proto/digraph.pro b/src/proto/digraph.pro
index dfadc9d..4c12f51 100644
--- a/src/proto/digraph.pro
+++ b/src/proto/digraph.pro
@@ -1,6 +1,6 @@
 /* digraph.c */
 int do_digraph(int c);
-char_u *get_digraph_for_char(int val);
+char_u *get_digraph_for_char(int val_arg);
 int get_digraph(int cmdline);
 int getdigraph(int char1, int char2, int meta_char);
 void putdigraph(char_u *str);