diff --git a/README.md b/README.md
index bc96b8b..d0450ed 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,8 @@ git clone https://github.com/TinkerBoard/gpio_lib_python.git
  sudo apt-get install python-dev python2.7-dev python3-dev\
  cd ASUS_GPIO_PYTHON_PATH/gpio/\
  sudo python setup.py install
+ * if encounter multiple definition error, use
+ `CFLAGS="-fcommon" python setup.py install`
 
 #A Simple Python Program\
  import ASUS.GPIO as GPIO\
diff --git a/source/py_gpio.c b/source/py_gpio.c
index 545f10c..97fe3ee 100644
--- a/source/py_gpio.c
+++ b/source/py_gpio.c
@@ -280,11 +280,11 @@ static PyObject *py_setup_channel(PyObject *self, PyObject *args, PyObject *kwar
 		return NULL;
 		chanlist = NULL;
 	} 
-	else if PyList_Check(chanlist) 
+	else if (PyList_Check(chanlist))
 	{
 		// do nothing
 	} 
-	else if PyTuple_Check(chanlist) 
+	else if (PyTuple_Check(chanlist))
 	{
 		chantuple = chanlist;
 		chanlist = NULL;
diff --git a/source/py_gpio_RPi.c b/source/py_gpio_RPi.c
index a1c739c..527d98b 100644
--- a/source/py_gpio_RPi.c
+++ b/source/py_gpio_RPi.c
@@ -273,11 +273,11 @@ static PyObject *py_setup_channel(PyObject *self, PyObject *args, PyObject *kwar
 		return NULL;
 		chanlist = NULL;
 	} 
-	else if PyList_Check(chanlist) 
+	else if (PyList_Check(chanlist))
 	{
 		// do nothing
 	} 
-	else if PyTuple_Check(chanlist) 
+	else if (PyTuple_Check(chanlist))
 	{
 		chantuple = chanlist;
 		chanlist = NULL;