diff --git a/src/webgpu/shader/validation/expression/matrix/mul.spec.ts b/src/webgpu/shader/validation/expression/matrix/mul.spec.ts
index e76e40265e09..a3a5d368dc2d 100644
--- a/src/webgpu/shader/validation/expression/matrix/mul.spec.ts
+++ b/src/webgpu/shader/validation/expression/matrix/mul.spec.ts
@@ -631,7 +631,7 @@ g.test('overflow_mat_f16_internal')
     for (let i = 0; i < t.params.c; i++) {
       for (let k = 0; k < t.params.r; k++) {
         lhs += `${t.params.lhs},`;
-        rhs += `1`;
+        rhs += `1,`;
       }
     }
     rhs += ')';