diff --git a/src/tools.c b/src/tools.c
index da0c8d7..746e0d0 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -1935,7 +1935,8 @@
 
 /*
  * Tries to prefix characters tagged in the <map> with the <escape>
- * character. The input <string> must be zero-terminated. The result will
+ * character. The input <string> is processed until string_stop
+ * is reached or NULL-byte is encountered. The result will
  * be stored between <start> (included) and <stop> (excluded). This
  * function will always try to terminate the resulting string with a '\0'
  * before <stop>, and will return its position if the conversion
@@ -1943,11 +1944,11 @@
  */
 char *escape_string(char *start, char *stop,
 		    const char escape, const long *map,
-		    const char *string)
+		    const char *string, const char *string_stop)
 {
 	if (start < stop) {
 		stop--; /* reserve one byte for the final '\0' */
-		while (start < stop && *string != '\0') {
+		while (start < stop && string < string_stop && *string != '\0') {
 			if (!ha_bit_test((unsigned char)(*string), map))
 				*start++ = *string;
 			else {