diff --git a/core/src/template-string/parser.pegjs b/core/src/template-string/parser.pegjs
index dce9954cce..a71456902e 100644
--- a/core/src/template-string/parser.pegjs
+++ b/core/src/template-string/parser.pegjs
@@ -187,7 +187,7 @@ Arguments
     }
 
 ArgumentList
-  = head:Expression tail:(__ "," __ Expression)* {
+  = head:PrimaryExpression tail:(__ "," __ PrimaryExpression)* {
       return buildList(head, tail, 3);
     }
 
diff --git a/core/test/unit/src/template-string.ts b/core/test/unit/src/template-string.ts
index 6e5b046d91..43ef4d8010 100644
--- a/core/test/unit/src/template-string.ts
+++ b/core/test/unit/src/template-string.ts
@@ -1041,6 +1041,11 @@ describe("resolveTemplateString", async () => {
       expect(res).to.equal("Zm9v")
     })
 
+    it("resolves a template string in a helper argument", () => {
+      const res = resolveTemplateString("${base64Encode('${a}')}", new TestContext({ a: "foo" }))
+      expect(res).to.equal("Zm9v")
+    })
+
     it("resolves a helper function with multiple arguments", () => {
       const res = resolveTemplateString("${split('a,b,c', ',')}", new TestContext({}))
       expect(res).to.eql(["a", "b", "c"])