--- src/search.c
+++ src/search.c
@@ -140,7 +140,7 @@ kwsmusts (void)
    are not single byte character nor the first byte of a multibyte
    character.  Caller must free the array.  */
 static char*
-check_multibyte_string(char const *buf, size_t size)
+check_multibyte_string(char const *buf, size_t size, int case_convert)
 {
   char *mb_properties = xmalloc(size);
   mbstate_t cur_state;
@@ -161,7 +161,7 @@ check_multibyte_string(char const *buf, 
 	     We treat it as a single byte character.  */
 	  mbclen = 1;
 	}
-      else if (match_icase)
+      else if (case_convert)
 	{
 	  if (iswupper((wint_t)wc))
 	    {
@@ -327,9 +327,9 @@ EXECUTE_FCT(EGexecute)
 	  if (start_ptr)
 	    start_ptr = case_buf + (start_ptr - buf);
           buf = case_buf;
+	  if (kwset)
+	    mb_properties = check_multibyte_string(buf, size, 1);
         }
-      if (kwset)
-        mb_properties = check_multibyte_string(buf, size);
     }
 #endif /* MBS_SUPPORT */
 
@@ -352,8 +352,13 @@ EXECUTE_FCT(EGexecute)
 	      end = memchr(beg, eol, buflim - beg);
 	      end++;
 #ifdef MBS_SUPPORT
-	      if (MB_CUR_MAX > 1 && mb_properties[beg - buf] == 0)
-		continue;
+	      if (MB_CUR_MAX > 1)
+		{
+		  if (!mb_properties)
+		    mb_properties = check_multibyte_string (buf, size, 0);
+		  if (mb_properties[beg - buf] == 0)
+		    continue;
+		}
 #endif
 	      while (beg > buf && beg[-1] != eol)
 		--beg;
@@ -543,8 +548,8 @@ EXECUTE_FCT(Fexecute)
 	  if (start_ptr)
 	    start_ptr = case_buf + (start_ptr - buf);
           buf = case_buf;
+	  mb_properties = check_multibyte_string(buf, size, 1);
         }
-      mb_properties = check_multibyte_string(buf, size);
     }
 #endif /* MBS_SUPPORT */
 
@@ -554,8 +559,13 @@ EXECUTE_FCT(Fexecute)
       if (offset == (size_t) -1)
 	goto failure;
 #ifdef MBS_SUPPORT
-      if (MB_CUR_MAX > 1 && mb_properties[offset+beg-buf] == 0)
-	continue; /* It is a part of multibyte character.  */
+      if (MB_CUR_MAX > 1)
+	{
+	  if (!mb_properties)
+	    mb_properties = check_multibyte_string(buf, size, 0);
+	  if (mb_properties[offset+beg-buf] == 0)
+	    continue; /* It is a part of multibyte character.  */
+	}
 #endif /* MBS_SUPPORT */
       beg += offset;
       len = kwsmatch.size[0];