1 files changed, 13 insertions, 3 deletions
diff --git a/ui/widgets/mouse.js b/ui/widgets/mouse.js
index 938d0f4b7..c14aebe53 100644
--- a/ui/widgets/mouse.js
+++ b/ui/widgets/mouse.js
@@ -8,7 +8,7 @@
  */
 
 //>>label: Mouse
-//>>group: UI Core
+//>>group: Widgets
 //>>description: Abstracts mouse-based interactions to assist in creating certain widgets.
 //>>docs: http://api.jqueryui.com/mouse/
 
@@ -146,7 +146,16 @@ return $.widget( "ui.mouse", {
 
 			// Iframe mouseup check - mouseup occurred in another document
 			} else if ( !event.which ) {
-				return this._mouseUp( event );
+
+				// Support: Safari <=8 - 9
+				// Safari sets which to 0 if you press any of the following keys
+				// during a drag (#14461)
+				if ( event.originalEvent.altKey || event.originalEvent.ctrlKey ||
+						event.originalEvent.metaKey || event.originalEvent.shiftKey ) {
+					this.ignoreMissingWhich = true;
+				} else if ( !this.ignoreMissingWhich ) {
+					return this._mouseUp( event );
+				}
 			}
 		}
 
@@ -188,8 +197,9 @@ return $.widget( "ui.mouse", {
 			delete this._mouseDelayTimer;
 		}
 
+		this.ignoreMissingWhich = false;
 		mouseHandled = false;
-		return false;
+		event.preventDefault();
 	},
 
 	_mouseDistanceMet: function( event ) {