--- a/pslab/external/AD9833.py
+++ b/pslab/external/AD9833.py
@@ -2,7 +2,7 @@
 
 
 class AD9833:
-    if sys.version.major == 3:
+    if sys.version_info.major == 3:
         DDS_MAX_FREQ = 0xFFFFFFF - 1  # 24 bit resolution
     else:
         DDS_MAX_FREQ = eval("0xFFFFFFFL-1")  # 24 bit resolution