Use of undeclared identifier 'UnityOnSetCurrentGLContext'?

I recently updated my project from 5.5.0p4 to 5.5.3p3. When I export for iOS and attempt to build in XCode, I get the following errors:

 EAGLContextHelper.mm:41:9: Use of undeclared identifier 'UnityOnSetCurrentGLContext'
 EAGLContextHelper.mm:52:9: Use of undeclared identifier 'UnityOnSetCurrentGLContext'
 EAGLContextHelper.mm:61:9: Use of undeclared identifier 'UnityOnSetCurrentGLContext'

I've compared the EAGLContextHelper.mm file generated by 5.5.0 vs 5.5.3, and the only significant difference is the addition of these three calls to 'UnityOnSetCurrentGLContext()'.

What am I doing wrong? Is there some way to declare this missing function?

Any advice would be appreciated.