diff --git a/changelog.txt b/changelog.txt
index ed49d13d..e0a71be4 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -3,7 +3,6 @@ OPENSEADRAGON CHANGELOG
 
 1.0.0: (in progress)
 
-* BREAKING CHANGE: TileSource 'ready' event handler signature changed for consistency to 'handlerMethod( eventSource, eventData)' (#239)
 * BREAKING CHANGE: Renamed EventHandler to EventSource (#225)
 * BREAKING CHANGE: MouseTracker event handler method signatures changed to 'handlerMethod( tracker, eventData)' (#23)
 * BREAKING CHANGE: Event names changed for consistency: changed to lower case, compound names hyphenated, and "on" prefixes removed (#226):
@@ -16,6 +15,8 @@ OPENSEADRAGON CHANGELOG
 *     Button "onExit" changed to "exit"
 *     Button "onFocus" changed to "focus"
 *     Button "onBlur" changed to "blur"
+* BREAKING CHANGE: Button event handler method signatures changed to 'handlerMethod( eventSource, eventData)' where eventData == { button } (#224)
+* BREAKING CHANGE: TileSource 'ready' event handler signature changed to 'handlerMethod( eventSource, eventData)' where eventData == { tileSource } (#239)
 * MouseTracker now passes the original event objects to its handler methods (#23)
 * MouseTracker now supports an optional 'moveHandler' method for tracking mousemove events (#215)
 * Fixed: Element-relative mouse coordinates now correct if the element and/or page is scrolled (using new OpenSeadragon.getElementOffset() method) (#131)
diff --git a/src/button.js b/src/button.js
index 062abf8a..cc7febb7 100644
--- a/src/button.js
+++ b/src/button.js
@@ -178,7 +178,7 @@ $.Button = function( options ) {
         enterHandler: function( tracker, eventData ) {
             if ( eventData.insideElementPressed ) {
                 inTo( _this, $.ButtonState.DOWN );
-                _this.raiseEvent( "enter", _this );
+                _this.raiseEvent( "enter", { button: _this } );
             } else if ( !eventData.buttonDownAny ) {
                 inTo( _this, $.ButtonState.HOVER );
             }
@@ -186,30 +186,30 @@ $.Button = function( options ) {
 
         focusHandler: function ( tracker, eventData ) {
             this.enterHandler( tracker, eventData );
-            _this.raiseEvent( "focus", _this );
+            _this.raiseEvent( "focus", { button: _this } );
         },
 
         exitHandler: function( tracker, eventData ) {
             outTo( _this, $.ButtonState.GROUP );
             if ( eventData.insideElementPressed ) {
-                _this.raiseEvent( "exit", _this );
+                _this.raiseEvent( "exit", { button: _this } );
             }
         },
 
         blurHandler: function ( tracker, eventData ) {
             this.exitHandler( tracker, eventData );
-            _this.raiseEvent( "blur", _this );
+            _this.raiseEvent( "blur", { button: _this } );
         },
 
         pressHandler: function ( tracker, eventData ) {
             inTo( _this, $.ButtonState.DOWN );
-            _this.raiseEvent( "press", _this );
+            _this.raiseEvent( "press", { button: _this } );
         },
 
         releaseHandler: function( tracker, eventData ) {
             if ( eventData.insideElementPressed && eventData.insideElementReleased ) {
                 outTo( _this, $.ButtonState.HOVER );
-                _this.raiseEvent( "release", _this );
+                _this.raiseEvent( "release", { button: _this } );
             } else if ( eventData.insideElementPressed ) {
                 outTo( _this, $.ButtonState.GROUP );
             } else {
@@ -219,15 +219,15 @@ $.Button = function( options ) {
 
         clickHandler: function( tracker, eventData ) {
             if ( eventData.quick ) {
-                _this.raiseEvent("click", _this);
+                _this.raiseEvent("click", { button: _this });
             }
         },
 
         keyHandler: function( tracker, eventData ){
             //console.log( "%s : handling key %s!", _this.tooltip, eventData.keyCode);
             if( 13 === eventData.keyCode ){
-                _this.raiseEvent( "click", _this );
-                _this.raiseEvent( "release", _this );
+                _this.raiseEvent( "click", { button: _this } );
+                _this.raiseEvent( "release", { button: _this } );
                 return false;
             }
             return true;