diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index d8e2487..2cde1ee 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -1700,7 +1700,13 @@
 	case GDK_SCROLL_DOWN:
 	    button = MOUSE_5;
 	    break;
-	default: /* We don't care about left and right...  Yet. */
+	case GDK_SCROLL_LEFT:
+	    button = MOUSE_7;
+	    break;
+	case GDK_SCROLL_RIGHT:
+	    button = MOUSE_6;
+	    break;
+	default: /* This shouldn't happen */
 	    return FALSE;
     }