diff --git a/handler.go b/handler.go
index 33d2e5846..bc6c625ef 100644
--- a/handler.go
+++ b/handler.go
@@ -108,7 +108,7 @@ func BuildRouters(handler *Handler) {
 
 func (h *Handler) populateValidators() {
 	h.validators = map[string]*queryValidationSpec{}
-	h.validators["GetFragmentNodes"] = queryValidationSpecRequired("slice").Optional("index")
+	h.validators["GetFragmentNodes"] = queryValidationSpecRequired("slice", "index")
 	h.validators["GetSliceMax"] = queryValidationSpecRequired().Optional("inverse")
 	h.validators["PostQuery"] = queryValidationSpecRequired().Optional("slices", "columnAttrs", "excludeAttrs", "excludeBits")
 	h.validators["GetExport"] = queryValidationSpecRequired("index", "frame", "view", "slice")
diff --git a/handler_test.go b/handler_test.go
index c7d2a80b7..063421667 100644
--- a/handler_test.go
+++ b/handler_test.go
@@ -1227,6 +1227,13 @@ func TestHandler_Fragment_Nodes(t *testing.T) {
 		t.Fatalf("unexpected status code: %d", w.Code)
 	}
 
+	// index is required
+	w = httptest.NewRecorder()
+	r = test.MustNewHTTPRequest("GET", "/fragment/nodes?slice=0", nil)
+	h.ServeHTTP(w, r)
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("unexpected status code: %d", w.Code)
+	}
 }
 
 // Ensure the handler can return expvars without panicking.