diff --git a/src/os/macosx/macos.h b/src/os/macosx/macos.h
--- a/src/os/macosx/macos.h
+++ b/src/os/macosx/macos.h
@@ -38,6 +38,8 @@ bool IsMonospaceFont(CFStringRef name);
 
 void MacOSSetThreadName(const char *name);
 
+uint64 MacOSGetPhysicalMemory();
+
 
 /** Deleter that calls CFRelease rather than deleting the pointer. */
 template <typename T> struct CFDeleter {