diff --git a/src/gam/__init__.py b/src/gam/__init__.py
index 5c5406e6..76f251ba 100755
--- a/src/gam/__init__.py
+++ b/src/gam/__init__.py
@@ -728,8 +728,12 @@ def getOSPlatform():
     elif myos == 'Darwin':
         myos = 'MacOS'
         mac_ver = platform.mac_ver()[0]
+        major_ver = int(mac_ver.split('.')[0])  # macver 10.14.6 == major_ver 10
         minor_ver = int(mac_ver.split('.')[1])  # macver 10.14.6 == minor_ver 14
-        codename = MACOS_CODENAMES.get(minor_ver, '')
+        if major_ver == 10:
+            codename = MACOS_CODENAMES[major_ver].get(minor_ver, '')
+        else:
+            codename = MACOS_CODENAMES.get(major_ver, '')
         pltfrm = ' '.join([codename, mac_ver])
     else:
         pltfrm = platform.platform()
diff --git a/src/gam/var.py b/src/gam/var.py
index 4c8f4ade..74bfec15 100644
--- a/src/gam/var.py
+++ b/src/gam/var.py
@@ -616,17 +616,21 @@ GOOGLEDOC_VALID_EXTENSIONS_MAP = {
 }
 
 MACOS_CODENAMES = {
-    6: 'Snow Leopard',
-    7: 'Lion',
-    8: 'Mountain Lion',
-    9: 'Mavericks',
-    10: 'Yosemite',
-    11: 'El Capitan',
-    12: 'Sierra',
-    13: 'High Sierra',
-    14: 'Mojave',
-    15: 'Catalina'
-}
+    10: {
+        6:  'Snow Leopard',
+        7:  'Lion',
+        8:  'Mountain Lion',
+        9:  'Mavericks',
+        10: 'Yosemite',
+        11: 'El Capitan',
+        12: 'Sierra',
+        13: 'High Sierra',
+        14: 'Mojave',
+        15: 'Catalina',
+        16: 'Big Sur'
+        },
+    11: 'Big Sur',
+    }
 
 _MICROSOFT_FORMATS_LIST = [{
     'mime':