--- a/VersionDiffBrowser.st	Sun Feb 01 22:54:05 2015 +0100
+++ b/VersionDiffBrowser.st	Mon Feb 02 09:33:40 2015 +0100
@@ -11,6 +11,8 @@
 "
 "{ Package: 'stx:libtool' }"
 
+"{ NameSpace: Smalltalk }"
+
 ApplicationModel subclass:#VersionDiffBrowser
 	instanceVariableNames:'classChangeSet diffTextView boxAVisible boxBVisible boxMVisible
 		classIfSingleClassDiff versionAIfSingleClassDiff
@@ -2506,11 +2508,16 @@
     theSourceCodeManager := SourceCodeManagerUtilities sourceCodeManagerFor:aClass.
     [
         theSourceStream := theSourceCodeManager getSourceStreamFor:aClass revision:aVersion.
-        theSourceStream notNil
-            ifTrue:[theChangeSet := ChangeSet fromStream:theSourceStream]
+        theSourceStream notNil ifTrue:[
+            theChangeSet := ChangeSet fromStream:theSourceStream
+        ]
     ] ensure:[
         theSourceStream notNil ifTrue:[theSourceStream close]
     ].
+    theChangeSet isNil ifTrue:[
+        self error:'Could not read source of class ',aClass name mayProceed:true.
+        ^ nil
+    ].
     self sortChangeSet:theChangeSet.
     ^ theChangeSet
 
@@ -2526,12 +2533,16 @@
     |theChangeSet theSourceStream|
 
     [
-	theSourceStream := aSource readStream.
-	theChangeSet := ChangeSet fromStream:(theSourceStream := aSource readStream)
+        theSourceStream := aSource readStream.
+        theChangeSet := ChangeSet fromStream:(theSourceStream := aSource readStream)
     ] ensure:[
-	theSourceStream notNil ifTrue:[
-	    theSourceStream close
-	]
+        theSourceStream notNil ifTrue:[
+            theSourceStream close
+        ]
+    ].
+    theChangeSet isNil ifTrue:[
+        self error:'Could not read source of class ',aClass name mayProceed:true.
+        ^ nil
     ].
     self sortChangeSet:theChangeSet.
     ^ theChangeSet
@@ -2871,10 +2882,10 @@
 !VersionDiffBrowser class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libtool/VersionDiffBrowser.st,v 1.121 2014-05-14 10:02:21 stefan Exp $'
+    ^ '$Header: /cvs/stx/stx/libtool/VersionDiffBrowser.st,v 1.122 2015-02-02 08:33:40 cg Exp $'
 !
 
 version_CVS
-    ^ '$Header: /cvs/stx/stx/libtool/VersionDiffBrowser.st,v 1.121 2014-05-14 10:02:21 stefan Exp $'
+    ^ '$Header: /cvs/stx/stx/libtool/VersionDiffBrowser.st,v 1.122 2015-02-02 08:33:40 cg Exp $'
 ! !