diff --git a/generate-gnostic/generate-extension.go b/generate-gnostic/generate-extension.go
index b8456185..27270d30 100644
--- a/generate-gnostic/generate-extension.go
+++ b/generate-gnostic/generate-extension.go
@@ -281,6 +281,9 @@ func generateExtension(schemaFile string, outDir string) error {
 		return err
 	}
 	err = exec.Command(runtime.GOROOT()+"/bin/gofmt", "-w", goFilename).Run()
+	if err != nil {
+		return err
+	}
 
 	// generate the main file.
 
diff --git a/generate-gnostic/generate-extension_test.go b/generate-gnostic/generate-extension_test.go
index 9ec62be5..344848f8 100644
--- a/generate-gnostic/generate-extension_test.go
+++ b/generate-gnostic/generate-extension_test.go
@@ -16,6 +16,9 @@ func TestErrorExtensionGeneratorUnsupportedPrimitive(t *testing.T) {
 		"test/x-unsupportedprimitives.json",
 		"--out_dir=/tmp",
 	).Output()
+	if err != nil {
+		t.Fatalf("error executing generate-gnostic: %v", err)
+	}
 
 	outputFile := "x-unsupportedprimitives.errors"
 	_ = ioutil.WriteFile(outputFile, output, 0644)
@@ -38,6 +41,9 @@ func TestErrorExtensionGeneratorNameCollision(t *testing.T) {
 		"test/x-extension-name-collision.json",
 		"--out_dir=/tmp",
 	).Output()
+	if err != nil {
+		t.Fatalf("error executing generate-gnostic: %v", err)
+	}
 
 	outputFile := "x-extension-name-collision.errors"
 	_ = ioutil.WriteFile(outputFile, output, 0644)