diff --git a/src/frontend/inpcom.c b/src/frontend/inpcom.c
index e7a8465c2..bdd3f4b58 100644
--- a/src/frontend/inpcom.c
+++ b/src/frontend/inpcom.c
@@ -4029,7 +4029,7 @@ inp_split_multi_param_lines(struct line *card, int line_num)
 
 
 static int
-identifier_char(int c)
+identifier_char(char c)
 {
     return (c == '_') || isalnum(c);
 }