diff --git a/modules/@angular/router/src/router.ts b/modules/@angular/router/src/router.ts
index b314711bc0..1b18b566c5 100644
--- a/modules/@angular/router/src/router.ts
+++ b/modules/@angular/router/src/router.ts
@@ -400,7 +400,9 @@ class PreActivation {
           if (s instanceof CanActivate) {
             return this.runCanActivate(s.route);
           } else if (s instanceof CanDeactivate) {
-            return this.runCanDeactivate(s.component, s.route);
+            // workaround https://github.com/Microsoft/TypeScript/issues/7271
+            const s2 = s as CanDeactivate;
+            return this.runCanDeactivate(s2.component, s2.route);
           } else {
             throw new Error('Cannot be reached');
           }