diff --git a/data/get_nndc_data.py b/data/get_nndc_data.py
index ec031b95f..aaaacd4df 100755
--- a/data/get_nndc_data.py
+++ b/data/get_nndc_data.py
@@ -32,7 +32,10 @@ for f in files:
     req = urlopen(url)
 
     # Get file size from header
-    file_size = int(req.info().getheaders('Content-Length')[0])
+    if sys.version_info[0] < 3:
+        file_size = int(req.info().getheaders('Content-Length')[0])
+    else:
+        file_size = req.length
     downloaded = 0
 
     # Check if file already downloaded