XGBRegressor, GammaRegression:label must be positive

My code is below:
def train():

train_factors, train_label = get_train_example('cu')

X_train, X_test, y_train, y_test = train_test_split(train_factors, train_label, test_size=0.2, random_state=0)

model = xgb.XGBRegressor(max_depth=6, learning_rate=0.1, n_estimators=160, silent=True, objective='reg:gamma')

model.fit(X_train, y_train)

ans = model.predict(X_test)

predict_series = pd.Series(list(ans))

label_series = pd.Series(list(train_label))

ic = predict_series.corr(label_series)

print('ic:' + str(ic))

There are negative data in my training data, is it forbiddened?

Yes, all labels must be strictly positive.