diff --git a/docs/sources/project/building_from_source.md b/docs/sources/project/building_from_source.md
index d4eb1a917d6..35e840d6e88 100644
--- a/docs/sources/project/building_from_source.md
+++ b/docs/sources/project/building_from_source.md
@@ -83,7 +83,7 @@ go get github.com/Unknwon/bra
 bra run
 ```
 
-You'll also need to run `yarn watch` to watch for changes to the front-end (typescript, html, sass)
+You'll also need to run `yarn start` to watch for changes to the front-end (typescript, html, sass)
 
 ### Running tests
 
diff --git a/public/app/plugins/datasource/prometheus/datasource.ts b/public/app/plugins/datasource/prometheus/datasource.ts
index a4f4ceb55d7..e4028e2687e 100644
--- a/public/app/plugins/datasource/prometheus/datasource.ts
+++ b/public/app/plugins/datasource/prometheus/datasource.ts
@@ -396,6 +396,10 @@ export class PrometheusDatasource implements DataSourceApi<PromQuery> {
       const expandedQueries = queries.map(query => ({
         ...query,
         expr: this.templateSrv.replace(query.expr, {}, this.interpolateQueryExpr),
+
+        // null out values we don't support in Explore yet
+        legendFormat: null,
+        step: null,
       }));
       state = {
         ...state,