1 files changed, 16 insertions, 11 deletions

diff --git a/regcomp.c b/regcomp.c
index de44cfe037..69a63011d1 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -3950,17 +3950,22 @@ optimize_node_left(Node* node, NodeOptInfo* opt, OptEnv* env)
 	}
       }
 
-      if (! ONIGENC_IS_SINGLEBYTE(env->enc)) {
-        if (! IS_NULL(cc->mbuf) ||
-            (cc->not != 0 && found != 0)) {
-          for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
-            z = ONIGENC_IS_MBC_HEAD(env->enc, i);
-            if (z) {
-              mb_found = 1;
-              add_char_opt_map_info(&opt->map, i);
-            }
-          }
-        }
+      if (IS_NULL(cc->mbuf)) {
+	if (cc->not) {
+	  for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
+	    add_char_opt_map_info(&opt->map, i);
+	  }
+	  mb_found = 1;
+	}
+      }
+      else {
+	for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
+	  z = ONIGENC_IS_MBC_HEAD(env->enc, i);
+	  if (z) {
+	    mb_found = 1;
+	    add_char_opt_map_info(&opt->map, i);
+	  }
+	}
       }
 
       if (mb_found) {