diff --git a/Quake/keys.c b/Quake/keys.c
index 92074032..a35385b4 100644
--- a/Quake/keys.c
+++ b/Quake/keys.c
@@ -119,6 +119,8 @@ keyname_t keynames[] =
 	{"MOUSE1", K_MOUSE1},
 	{"MOUSE2", K_MOUSE2},
 	{"MOUSE3", K_MOUSE3},
+	{"MOUSE4", K_MOUSE4},
+	{"MOUSE5", K_MOUSE5},
 
 	{"JOY1", K_JOY1},
 	{"JOY2", K_JOY2},
diff --git a/Quake/keys.h b/Quake/keys.h
index 35841ed4..4ae71705 100644
--- a/Quake/keys.h
+++ b/Quake/keys.h
@@ -139,6 +139,10 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #define K_MWHEELUP		239
 #define K_MWHEELDOWN		240
 
+// thumb buttons
+#define K_MOUSE4		241
+#define K_MOUSE5		242
+
 
 typedef enum {key_game, key_console, key_message, key_menu} keydest_t;
 
diff --git a/Quake/main_sdl.c b/Quake/main_sdl.c
index 77e65e2b..9e562111 100644
--- a/Quake/main_sdl.c
+++ b/Quake/main_sdl.c
@@ -130,6 +130,12 @@ int main(int argc, char *argv[])
 			  case SDL_BUTTON_WHEELDOWN:
 				Key_Event(K_MWHEELDOWN, event.button.type == SDL_MOUSEBUTTONDOWN);
 				break;
+			  case SDL_BUTTON_X1:
+				Key_Event(K_MOUSE4, event.button.type == SDL_MOUSEBUTTONDOWN);
+				break;
+			  case SDL_BUTTON_X2:
+				Key_Event(K_MOUSE5, event.button.type == SDL_MOUSEBUTTONDOWN);
+				break;
 			  }
 			  break;
 			case SDL_KEYDOWN: