diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 15547bb..f631f60 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -1307,7 +1307,7 @@
 		    rc_did_emsg = TRUE;
 		    return FAIL;
 		}
-		siemsg("INTERNAL: Unknown character class char: %ld", c);
+		siemsg("INTERNAL: Unknown character class char: %d", c);
 		return FAIL;
 	    }
 #ifdef FEAT_MBYTE