diff --git a/src/jv.c b/src/jv.c
index f051d730..b3fcd5e3 100644
--- a/src/jv.c
+++ b/src/jv.c
@@ -658,6 +658,8 @@ jv jv_string_indexes(jv j, jv k) {
   int idxlen = jv_string_length_bytes(jv_copy(k));
   jv a = jv_array();
 
+  if (idxlen == 0)
+    return a;
   p = jstr;
   while ((p = _jq_memmem(p, (jstr + jlen) - p, idxstr, idxlen)) != NULL) {
     a = jv_array_append(a, jv_number(p - jstr));
diff --git a/tests/jq.test b/tests/jq.test
index 6ee657b6..1572043e 100644
--- a/tests/jq.test
+++ b/tests/jq.test
@@ -1538,4 +1538,9 @@ isempty(1,error("foo"))
 null
 false
 
+# Regression test for #1815
+index("")
+""
+null
+