diff --git a/src/njs_vmcode.c b/src/njs_vmcode.c
index ec478659..ac03fa32 100644
--- a/src/njs_vmcode.c
+++ b/src/njs_vmcode.c
@@ -1056,6 +1056,11 @@ njs_vmcode_array(njs_vm_t *vm, u_char *pc)
         if (code->ctor) {
             /* Array of the form [,,,], [1,,]. */
             if (array->object.fast_array) {
+                if (njs_slow_path(array->start == NULL)) {
+                    njs_stderror("ARRAYLIT-GUARD fill loop reached with "
+                                 "NULL start\n");
+                    abort();
+                }
                 value = array->start;
                 length = array->length;