diff --git a/tools/@angular/tsc-wrapped/src/symbols.ts b/tools/@angular/tsc-wrapped/src/symbols.ts
index 474cbd0b8b..c3d96145f0 100644
--- a/tools/@angular/tsc-wrapped/src/symbols.ts
+++ b/tools/@angular/tsc-wrapped/src/symbols.ts
@@ -16,7 +16,7 @@ export class Symbols {
   private get symbols(): Map<string, MetadataValue> {
     let result = this._symbols;
     if (!result) {
-      result = this._symbols = new Map();
+      result = this._symbols = new Map<string, MetadataValue>();
       populateBuiltins(result);
       this.buildImports();
     }
@@ -110,4 +110,4 @@ function populateBuiltins(symbols: Map<string, MetadataValue>) {
    'Uint8ClampedArray', 'Uint16Array', 'Int16Array', 'Int32Array', 'Uint32Array', 'Float32Array',
    'Float64Array']
       .forEach(name => symbols.set(name, {__symbolic: 'reference', name}));
-}
\ No newline at end of file
+}