Package Compile Error

Another programmer sent me a code for a new(not an update to an existing) package and asked me to compile it into our Oracle database.  I connected to the dev database, opened his package from a text file and compiled it in SQL Developer.  I was in a bit of a hurry and didn't play too close attention, but the package compiled with no errors. 

I wanted to rename the package before checking it into our code repository, so I dropped the package which I had created and tried compiling it with the new package name in CREATE OR REPLACE PACKAGE BODY line and in the final line of the package.  Now I'm getting a compile error due to a missing package spec.  I didn't have a corresponding package spec when I originally the package the programmer supplied, but didn't receive this error.  Can anyone explain why I might be receiving the error now, but not previoiusly?