diff --git a/osdp/_connection.py b/osdp/_connection.py
index 813a346..98d4e6c 100644
--- a/osdp/_connection.py
+++ b/osdp/_connection.py
@@ -45,7 +45,7 @@ def baud_rate(self) -> int:
 
 	@property
 	def is_open(self) -> bool:
-		self.serial_port is not None and self.serial_port.is_open
+		return self.serial_port is not None and self.serial_port.is_open
 
 	def open(self):
 		self.serial_port = serial.Serial(port=self._port, baudrate=self._baud_rate, timeout=2.0)
diff --git a/requirements.txt b/requirements.txt
index c21b6ec..30d09d5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1,2 @@
-pycryptodome
\ No newline at end of file
+pycryptodome
+pyserial
\ No newline at end of file