--- plugins/adplug/adplug/s3m.cpp
+++ plugins/adplug/adplug/s3m.cpp
@@ -26,7 +26,7 @@
 #include <string.h>
 #include "s3m.h"
 
-const char Cs3mPlayer::chnresolv[] =	// S3M -> adlib channel conversion
+const signed char Cs3mPlayer::chnresolv[] =	// S3M -> adlib channel conversion
   {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,0,1,2,3,4,5,6,7,8,-1,-1,-1,-1,-1,-1,-1};
 
 const unsigned short Cs3mPlayer::notetable[12] =		// S3M adlib note table
--- plugins/adplug/adplug/s3m.h
+++ plugins/adplug/adplug/s3m.h
@@ -92,7 +92,7 @@ class Cs3mPlayer: public CPlayer
   char filetype[30];
 
  private:
-  static const char chnresolv[];
+  static const signed char chnresolv[];
   static const unsigned short notetable[12];
   static const unsigned char vibratotab[32];