diff --git a/src/subr.c b/src/subr.c
index e8d7255..6d7fc0f 100755
--- a/src/subr.c
+++ b/src/subr.c
@@ -92,7 +92,7 @@ char *atom_to_str(LispPTR atom_index)
 		}							\
 }
 
-OP_subrcall(int subr_no, int argnum)
+void OP_subrcall(int subr_no, int argnum)
 {
   static LispPTR args[30];
   int  arg_num;