diff --git a/constants.h b/constants.h
index 718042c..61e325b 100644
--- a/constants.h
+++ b/constants.h
@@ -159,6 +159,8 @@ enum RDP_INPUT_DEVICE
 #define MOUSE_FLAG_BUTTON1      0x1000
 #define MOUSE_FLAG_BUTTON2      0x2000
 #define MOUSE_FLAG_BUTTON3      0x4000
+#define MOUSE_FLAG_BUTTON4      0x0280
+#define MOUSE_FLAG_BUTTON5      0x0380
 #define MOUSE_FLAG_DOWN         0x8000
 
 /* Raster operation masks */
diff --git a/xkeymap.c b/xkeymap.c
index 1b738b2..71cddcb 100644
--- a/xkeymap.c
+++ b/xkeymap.c
@@ -183,6 +183,10 @@ uint16 xkeymap_translate_button(unsigned int button)
 			return MOUSE_FLAG_BUTTON3;
 		case Button3:   /* right */
 			return MOUSE_FLAG_BUTTON2;
+		case Button4:   /* wheel up */
+			return MOUSE_FLAG_BUTTON4;
+		case Button5:   /* wheel down */
+			return MOUSE_FLAG_BUTTON5;
 	}
 
 	return 0;