diff --git a/option/option.go b/option/option.go
index 74a2308..830c96d 100644
--- a/option/option.go
+++ b/option/option.go
@@ -73,7 +73,10 @@ func WithAPIToken(token string) ClientOption {
 // WithServiceAccount returns a ClientOption that specifies the credentials file to use.
 func WithServiceAccount(data []byte) ClientOption {
 	ts, sa, err := signer.NewServiceAccountTokenSource(data)
-	return withTokenSource{sa.ApiEndpoint, ts, err}
+	if err != nil {
+		return withTokenSource{"", nil, err}
+	}
+	return withTokenSource{sa.ApiEndpoint, ts, nil}
 }
 
 // WithServiceAccountFile returns a ClientOption that specifies the credentials file to use.
@@ -84,7 +87,10 @@ func WithServiceAccountFile(filename string) ClientOption {
 	}
 
 	ts, sa, err := signer.NewServiceAccountTokenSource(data)
-	return withTokenSource{sa.ApiEndpoint, ts, err}
+	if err != nil {
+		return withTokenSource{"", nil, err}
+	}
+	return withTokenSource{sa.ApiEndpoint, ts, nil}
 }
 
 // WithoutAuthentication returns a ClientOption that disables authentication.