diff --git a/packages/grafana-runtime/src/services/templateSrv.ts b/packages/grafana-runtime/src/services/templateSrv.ts
index 7b6fe6df195..36cc70df3a7 100644
--- a/packages/grafana-runtime/src/services/templateSrv.ts
+++ b/packages/grafana-runtime/src/services/templateSrv.ts
@@ -1,4 +1,4 @@
-import { VariableModel } from '@grafana/data';
+import { VariableModel, ScopedVars } from '@grafana/data';
 
 /**
  * Via the TemplateSrv consumers get access to all the available template variables
@@ -8,7 +8,15 @@ import { VariableModel } from '@grafana/data';
  * @public
  */
 export interface TemplateSrv {
+  /**
+   * List the dashboard variables
+   */
   getVariables(): VariableModel[];
+
+  /**
+   * Replace the values within the target string.  See also {@link InterpolateFunction}
+   */
+  replace(target: string, scopedVars?: ScopedVars, format?: string | Function): string;
 }
 
 let singletonInstance: TemplateSrv;
diff --git a/public/app/features/templating/template_srv.ts b/public/app/features/templating/template_srv.ts
index 52f66c8363c..df55841d912 100644
--- a/public/app/features/templating/template_srv.ts
+++ b/public/app/features/templating/template_srv.ts
@@ -317,7 +317,7 @@ export class TemplateSrv implements BaseTemplateSrv {
     return scopedVar.value;
   }
 
-  replace(target: string, scopedVars?: ScopedVars, format?: string | Function): any {
+  replace(target: string, scopedVars?: ScopedVars, format?: string | Function): string {
     if (!target) {
       return target;
     }
diff --git a/public/app/plugins/datasource/cloudwatch/datasource.ts b/public/app/plugins/datasource/cloudwatch/datasource.ts
index c7ce5491684..f1ea1ea48c2 100644
--- a/public/app/plugins/datasource/cloudwatch/datasource.ts
+++ b/public/app/plugins/datasource/cloudwatch/datasource.ts
@@ -300,7 +300,7 @@ export class CloudWatchDatasource extends DataSourceApi<CloudWatchQuery, CloudWa
   }
 
   getPeriod(target: CloudWatchMetricsQuery, options: any) {
-    let period = this.templateSrv.replace(target.period, options.scopedVars);
+    let period = this.templateSrv.replace(target.period, options.scopedVars) as any;
     if (period && period.toLowerCase() !== 'auto') {
       if (/^\d+$/.test(period)) {
         period = parseInt(period, 10);