diff --git a/src/string.c b/src/string.c
index 6eb5e18..1426def 100644
--- a/src/string.c
+++ b/src/string.c
@@ -62,6 +62,10 @@ char *string_replace_at(const char *src, unsigned int from, unsigned int to,
   unsigned long rpl_len;
   char *dst;
 
+  if (to < from) {
+    return "";
+  }
+
   src_len = strnlen(src, STR_LEN * STR_LEN);
   rpl_len = strnlen(rpl, STR_LEN * STR_LEN);