diff --git a/drivers/Serial.h b/drivers/Serial.h
index 7c5e536acb..4493c6f6f9 100644
--- a/drivers/Serial.h
+++ b/drivers/Serial.h
@@ -99,6 +99,7 @@ public:
         return SerialBase::writeable();
     }
 
+#if !(DOXYGEN_ONLY)
 protected:
     virtual int _getc();
     virtual int _putc(int c);
@@ -106,6 +107,7 @@ protected:
     virtual void unlock();
 
     PlatformMutex _mutex;
+#endif
 };
 
 } // namespace mbed