diff --git a/builder/googlecompute/config_test.go b/builder/googlecompute/config_test.go
index d7dd11ebc..b7c46ea56 100644
--- a/builder/googlecompute/config_test.go
+++ b/builder/googlecompute/config_test.go
@@ -399,17 +399,20 @@ func TestConfigPrepareIAP(t *testing.T) {
 		t.Fatalf("Shouldn't have errors. Err = %s", err)
 	}
 
-	if c.IAPHashBang != "/bin/sh" {
-		t.Fatalf("IAP hashbang didn't default correctly to /bin/sh.")
-	}
 	if runtime.GOOS == "windows" {
 		if c.IAPExt != ".cmd" {
 			t.Fatalf("IAP tempfile extension didn't default correctly to .cmd")
 		}
+		if c.IAPHashBang != "" {
+			t.Fatalf("IAP hashbang didn't default correctly to nothing.")
+		}
 	} else {
 		if c.IAPExt != "" {
 			t.Fatalf("IAP tempfile extension should default to empty on unix mahcines")
 		}
+		if c.IAPHashBang != "/bin/sh" {
+			t.Fatalf("IAP hashbang didn't default correctly to /bin/sh.")
+		}
 	}
 	if c.Comm.SSHHost != "localhost" {
 		t.Fatalf("Didn't correctly override the ssh host.")
diff --git a/builder/googlecompute/step_start_tunnel_test.go b/builder/googlecompute/step_start_tunnel_test.go
index 3cf65ac3b..47813df8e 100644
--- a/builder/googlecompute/step_start_tunnel_test.go
+++ b/builder/googlecompute/step_start_tunnel_test.go
@@ -67,7 +67,9 @@ gcloud config set project fake-project-123
 gcloud compute start-iap-tunnel fakeinstance-12345 1234 --local-host-port=localhost:8774 --zone us-central-b
 `
 	if runtime.GOOS == "windows" {
-		expected = `
+		// in real life you'd not be passing a HashBang here, but GIGO.
+		expected = `#!/bin/bash
+
 call gcloud auth activate-service-account --key-file "/path/to/account_file.json"
 call gcloud config set project fake-project-123
 call gcloud compute start-iap-tunnel fakeinstance-12345 1234 --local-host-port=localhost:8774 --zone us-central-b