diff --git a/ChangeLog b/ChangeLog
index fae8a27db..d4cdc5025 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2006-11-08  Richard Frith-Macdonald <rfm@gnu.org>
+
+	Source/NSIndexSet.m: ([addIndexesInRange:])
+	Fix for case when added range lies within existing range.
+
 2006-11-08  Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/Additions/GSXML.m: ([stringByEscapingXML]) Fix bug causing
diff --git a/Source/NSIndexSet.m b/Source/NSIndexSet.m
index d6864d540..8617b0fd1 100644
--- a/Source/NSIndexSet.m
+++ b/Source/NSIndexSet.m
@@ -673,9 +673,16 @@ static unsigned posForIndex(GSIArray array, unsigned index)
 	{
 	  break;
 	}
-      r.length += (NSMaxRange(aRange) - NSMaxRange(r));
-      GSIArrayRemoveItemAtIndex(_array, pos--);
-      GSIArraySetItemAtIndex(_array, (GSIArrayItem)r, pos);
+      if (NSMaxRange(r) >= NSMaxRange(aRange))
+        {
+          GSIArrayRemoveItemAtIndex(_array, pos--);
+	}
+      else
+        {
+          r.length += (NSMaxRange(aRange) - NSMaxRange(r));
+          GSIArrayRemoveItemAtIndex(_array, pos--);
+          GSIArraySetItemAtIndex(_array, (GSIArrayItem)r, pos);
+	}
     }
 
   /*