diff --git a/HISTORY.md b/HISTORY.md
index f697b393..bf7375c0 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -11,6 +11,9 @@
     * Norwegian, thanks, Olav!
     * German
 
+### 2020-09-04
+* byob, blocks, objects: refactored scanning for message senders 
+
 ### 2020-09-03
 * byob: experimental: Inspect & export dependencies for global custom blocks (shift-right-click for context menu)
 * byob: new feature: "export block definition" including dependencies
diff --git a/snap.html b/snap.html
index 15ca19e2..fc285fd8 100755
--- a/snap.html
+++ b/snap.html
@@ -8,13 +8,13 @@
         <script src="src/morphic.js?version=2020-07-23"></script>
         <script src="src/symbols.js?version=2020-07-21"></script>
         <script src="src/widgets.js?version=2020-07-27"></script>
-        <script src="src/blocks.js?version=2020-09-03"></script>
+        <script src="src/blocks.js?version=2020-09-04"></script>
         <script src="src/threads.js?version=2020-09-02"></script>
-        <script src="src/objects.js?version=2020-09-03"></script>
+        <script src="src/objects.js?version=2020-09-04"></script>
         <script src="src/gui.js?version=2020-09-01"></script>
         <script src="src/paint.js?version=2020-05-17"></script>
         <script src="src/lists.js?version=2020-07-01"></script>
-        <script src="src/byob.js?version=2020-09-03"></script>
+        <script src="src/byob.js?version=2020-09-04"></script>
         <script src="src/tables.js?version=2020-05-18"></script>
         <script src="src/sketch.js?version=2020-07-13"></script>
         <script src="src/video.js?version=2019-06-27"></script>
diff --git a/src/blocks.js b/src/blocks.js
index 75b7a7fa..1305afac 100644
--- a/src/blocks.js
+++ b/src/blocks.js
@@ -158,7 +158,7 @@ CustomCommandBlockMorph, SymbolMorph, ToggleButtonMorph, DialMorph*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.blocks = '2020-September-03';
+modules.blocks = '2020-September-04';
 
 var SyntaxElementMorph;
 var BlockMorph;
@@ -3173,6 +3173,37 @@ BlockMorph.prototype.showMessageUsers = function () {
     }
 };
 
+BlockMorph.prototype.isSending = function (message, receiverName, known = []) {
+    if (typeof message === 'number') {
+        message = message.toString();
+    }
+    return this.allChildren().some(morph => {
+        var event, eventReceiver;
+        if (morph.isCustomBlock &&
+                morph.isGlobal &&
+                    contains(known, morph.definition)
+        ) {
+            return true;
+        }
+        if ((morph.selector) &&
+                contains(
+                    ['doBroadcast', 'doBroadcastAndWait', 'doSend'],
+                    morph.selector)
+        ) {
+            event = morph.inputs()[0].evaluate();
+            if (morph.selector === 'doSend') {
+                eventReceiver = morph.inputs()[1].evaluate();
+            }
+            return ((morph.selector !== 'doSend') ||
+                    (receiverName === eventReceiver)) &&
+                ((event === message) ||
+                    (message instanceof Array &&
+                        message[0] === 'any message'));
+        }
+        return false;
+    });
+};
+
 BlockMorph.prototype.developersMenu = function () {
     var menu = BlockMorph.uber.developersMenu.call(this);
     menu.addLine();
diff --git a/src/byob.js b/src/byob.js
index b0460938..2ba20d1f 100644
--- a/src/byob.js
+++ b/src/byob.js
@@ -107,7 +107,7 @@ WatcherMorph, Variable, BooleanSlotMorph, XML_Serializer, SnapTranslator*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.byob = '2020-September-03';
+modules.byob = '2020-September-04';
 
 // Declarations
 
@@ -589,32 +589,9 @@ CustomBlockDefinition.prototype.collectDependencies = function (
 };
 
 CustomBlockDefinition.prototype.isSending = function (message, receiverName) {
-    if (typeof message === 'number') {
-        message = message.toString();
-    }
     return this.scripts.concat(
         this.body ? [this.body.expression] : []
-    ).some(script =>
-        script.allChildren().some(morph => {
-            var event, eventReceiver;
-            if ((morph.selector) &&
-                    contains(
-                        ['doBroadcast', 'doBroadcastAndWait', 'doSend'],
-                        morph.selector)
-            ) {
-                event = morph.inputs()[0].evaluate();
-                if (morph.selector === 'doSend') {
-                    eventReceiver = morph.inputs()[1].evaluate();
-                }
-                return ((morph.selector !== 'doSend') ||
-                        (receiverName === eventReceiver)) &&
-                    ((event === message) ||
-                        (message instanceof Array &&
-                            message[0] === 'any message'));
-            }
-            return false;
-        })
-    );
+    ).some(script => script.isSending(message, receiverName));
 };
 
 // CustomCommandBlockMorph /////////////////////////////////////////////
diff --git a/src/objects.js b/src/objects.js
index aee2b763..dcd744d4 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -84,7 +84,7 @@ BlockEditorMorph, BlockDialogMorph, PrototypeHatBlockMorph,  BooleanSlotMorph,
 localize, TableMorph, TableFrameMorph, normalizeCanvas, VectorPaintEditorMorph,
 HandleMorph, AlignmentMorph, Process, XML_Element, WorldMap, copyCanvas*/
 
-modules.objects = '2020-September-03';
+modules.objects = '2020-September-04';
 
 var SpriteMorph;
 var StageMorph;
@@ -5774,35 +5774,8 @@ SpriteMorph.prototype.allMessageNames = function () {
 };
 
 SpriteMorph.prototype.allSendersOf = function (message, receiverName, known) {
-    if (typeof message === 'number') {
-        message = message.toString();
-    }
     return this.allScripts().filter(script =>
-        script.allChildren().some(morph => {
-            var event, eventReceiver;
-            if (morph.isCustomBlock &&
-                    morph.isGlobal &&
-                        contains(known, morph.definition)
-            ) {
-                return true;
-            }
-            if ((morph.selector) &&
-                    contains(
-                        ['doBroadcast', 'doBroadcastAndWait', 'doSend'],
-                        morph.selector)
-            ) {
-                event = morph.inputs()[0].evaluate();
-                if (morph.selector === 'doSend') {
-                    eventReceiver = morph.inputs()[1].evaluate();
-                }
-                return ((morph.selector !== 'doSend') ||
-                        (receiverName === eventReceiver)) &&
-                    ((event === message) ||
-                        (message instanceof Array &&
-                            message[0] === 'any message'));
-            }
-            return false;
-        })
+        script.isSending(message, receiverName, known)
     );
 };