diff --git a/public/app/plugins/datasource/prometheus/datasource.ts b/public/app/plugins/datasource/prometheus/datasource.ts
index 41f78ec7421..2c7c62d881b 100644
--- a/public/app/plugins/datasource/prometheus/datasource.ts
+++ b/public/app/plugins/datasource/prometheus/datasource.ts
@@ -437,7 +437,7 @@ export class PrometheusDatasource {
   }
 
   getQueryHints(query: DataQuery, result: any[]) {
-    return getQueryHints(query.expr, result, this);
+    return getQueryHints(query.expr || '', result, this);
   }
 
   loadRules() {
diff --git a/public/app/plugins/datasource/prometheus/query_hints.ts b/public/app/plugins/datasource/prometheus/query_hints.ts
index ea505832468..ce019e3ddcb 100644
--- a/public/app/plugins/datasource/prometheus/query_hints.ts
+++ b/public/app/plugins/datasource/prometheus/query_hints.ts
@@ -96,7 +96,7 @@ export function getQueryHints(query: string, series?: any[], datasource?: any):
     }
   }
 
-  if (series.length >= SUM_HINT_THRESHOLD_COUNT) {
+  if (series && series.length >= SUM_HINT_THRESHOLD_COUNT) {
     const simpleMetric = query.trim().match(/^\w+$/);
     if (simpleMetric) {
       hints.push({