diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 418d8da..ec49b0d 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -2309,12 +2309,22 @@
   try:
     return int(version)
   except ValueError:
-    # Not a decimal number. Codename?
-    if version in codename_to_api_level_map:
-      return codename_to_api_level_map[version]
+    # Not a decimal number.
+    #
+    # It could be either a straight codename, e.g.
+    #     UpsideDownCake
+    #
+    # Or a codename with API fingerprint SHA, e.g.
+    #     UpsideDownCake.e7d3947f14eb9dc4fec25ff6c5f8563e
+    #
+    # Extract the codename and try and map it to a version number.
+    split = version.split(".")
+    codename = split[0]
+    if codename in codename_to_api_level_map:
+      return codename_to_api_level_map[codename]
     raise ExternalError(
-        "Unknown minSdkVersion: '{}'. Known codenames: {}".format(
-            version, codename_to_api_level_map))
+        "Unknown codename: '{}' from minSdkVersion: '{}'. Known codenames: {}".format(
+            codename, version, codename_to_api_level_map))
 
 
 def SignFile(input_name, output_name, key, password, min_api_level=None,