@@ -226,11 +226,11 @@
 	size_t i;
 
 	for (i = 0; i <= idx; i++)
 		if (OF_UNLIKELY((str[i] & 0xC0) == 0x80))
 			if (++idx > len)
-				return SIZE_MAX;
+				return OF_INVALID_INDEX;
 
 	return idx;
 }
 
 @implementation OFString
@@ -917,17 +917,17 @@
 
 	if (str_len == 0)
 		return 0;
 
 	if (str_len > length)
-		return SIZE_MAX;
+		return OF_INVALID_INDEX;
 
 	for (i = 0; i <= length - str_len; i++)
 		if (!memcmp(string + i, str_c, str_len))
 			return of_string_position_to_index(string, i);
 
-	return SIZE_MAX;
+	return OF_INVALID_INDEX;
 }
 
 - (size_t)indexOfLastOccurrenceOfString: (OFString*)str
 {
 	const char *str_c = [str cString];
@@ -936,19 +936,19 @@
 
 	if (str_len == 0)
 		return of_string_position_to_index(string, length);
 
 	if (str_len > length)
-		return SIZE_MAX;
+		return OF_INVALID_INDEX;
 
 	for (i = length - str_len;; i--) {
 		if (!memcmp(string + i, str_c, str_len))
 			return of_string_position_to_index(string, i);
 
 		/* Did not match and we're at the last char */
 		if (i == 0)
-			return SIZE_MAX;
+			return OF_INVALID_INDEX;
 	}
 }
 
 - (BOOL)containsString: (OFString*)str
 {