diff --git a/libraries/oplsynth/oplio.cpp b/libraries/oplsynth/oplio.cpp
index 1a7c93a43..e1b6e8644 100644
--- a/libraries/oplsynth/oplio.cpp
+++ b/libraries/oplsynth/oplio.cpp
@@ -26,6 +26,8 @@
 #include <math.h>
 #include <assert.h>
 #include <algorithm>
+#include <string.h>
+
 #include "genmidi.h"
 #include "oplio.h"
 #include "opl.h"
diff --git a/src/sound/mididevices/midi_cvars.cpp b/src/sound/mididevices/midi_cvars.cpp
index 99a9de6ea..4bba9b091 100644
--- a/src/sound/mididevices/midi_cvars.cpp
+++ b/src/sound/mididevices/midi_cvars.cpp
@@ -39,8 +39,10 @@
 #include "cmdlib.h"
 #include "doomerrors.h"
 
+#ifdef _WIN32
 // do this without including windows.h for this one single prototype
 extern "C" unsigned __stdcall GetSystemDirectoryA(char* lpBuffer, unsigned uSize);
+#endif // _WIN32
 
 static void CheckRestart(int devtype)
 {