Fallback handler could not load library Contents/Frameworks/MonoEmbedRuntime/osx/kernel32

I'm experiencing the following error when I try to run the standalone Mac build of my game:

 Fallback handler could not load library /Users/.../Library/Application Support/Steam/steamapps/common/Legion TD 2/Legion TD 2.app/Contents/Frameworks/MonoEmbedRuntime/osx/kernel32
 Fallback handler could not load library /Users/.../Library/Application Support/Steam/steamapps/common/Legion TD 2/Legion TD 2.app/Contents/Frameworks/MonoEmbedRuntime/osx/libkernel32.dylib
 Fallback handler could not load library /Users/.../Library/Application Support/Steam/steamapps/common/Legion TD 2/Legion TD 2.app/Contents/Frameworks/MonoEmbedRuntime/osx/libkernel32.so
 Fallback handler could not load library /Users/.../Library/Application Support/Steam/steamapps/common/Legion TD 2/Legion TD 2.app/Contents/Frameworks/MonoEmbedRuntime/osx/libkernel32.bundle
 Fallback handler could not load library /Users/.../Library/Application Support/Steam/steamapps/common/Legion TD 2/Legion TD 2.app/Contents/Frameworks/MonoEmbedRuntime/osx/kernel32.dylib
 Fallback handler could not load library /Users/.../Library/Application Support/Steam/steamapps/common/Legion TD 2/Legion TD 2.app/Contents/Frameworks/MonoEmbedRuntime/osx/kernel32.so

Standalone build for Windows x64 and x32 both work fine.

What is causing this and how can I fix it?