diff --git a/src/program.ts b/src/program.ts
index e1212b4dd4..ff7e30098a 100644
--- a/src/program.ts
+++ b/src/program.ts
@@ -3932,7 +3932,7 @@ export class Field extends VariableLikeElement {
   get internalSetterSignature(): Signature {
     var cached = this._internalSetterSignature;
     if (!cached) {
-      this._internalGetterSignature = cached = new Signature(this.program, [ this.type ], Type.void, this.thisType);
+      this._internalSetterSignature = cached = new Signature(this.program, [ this.type ], Type.void, this.thisType);
     }
     return cached;
   }