diff --git a/ChangeLog.md b/ChangeLog.md
index 6996b5f..40d6e8d 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -7,8 +7,17 @@ All notable changes to MIMWAL project will be documented in this file. The "Unre
 * Support for multi-valued attributes in `[//Effective]` lookup in AuthZ workflows.
 * Implement Approve Request Activity.
 * Support for `[//Value]` lookups in Query definitions across rest of the activities.
+------------
+
+### Version 2.19.0111.0
+
+#### Changed
+
+* [Generate Unique Value Activity][GenerateUniqueValueActivity] now has the Conflict Filter search optimisation logic for the *starts-with* XPath function as documented in the [Wiki](https://github.com/Microsoft/MIMWAL/wiki/Generate-Unique-Value-Activity#conflict-filter) turned off by default.
+To get the backward compatible behaviour, define the app setting GenerateUniqueValueActivity_OptimizeUniquenessKey = true in the FIMService app.config.
 
 ------------
+
 ### Version 2.18.1110.0
 
 #### Changed
@@ -278,3 +287,4 @@ All notable changes to MIMWAL project will be documented in this file. The "Unre
 [WordFunction]: https://github.com/Microsoft/MIMWAL/wiki/Word-Function
 [WrapXPathFilterFunction]: https://github.com/Microsoft/MIMWAL/wiki/WrapXPathFilter-Function
 [MIMWalFunctionsTable]: https://github.com/Microsoft/MIMWAL/wiki/Functions-Table
+[GenerateUniqueValueActivity]: https://github.com/Microsoft/MIMWAL/wiki/Generate-Unique-Value-Activity
diff --git a/src/VersionInfo.cs b/src/VersionInfo.cs
index a2695b7..9f9ea88 100644
--- a/src/VersionInfo.cs
+++ b/src/VersionInfo.cs
@@ -22,7 +22,7 @@ internal static class VersionInfo
         ///      Build Number (MMDD)
         ///      Revision (if any on the same day)
         /// </summary>
-        internal const string Version = "2.18.1110.0";
+        internal const string Version = "2.19.0111.0";
 
         /// <summary>
         /// File Version information for the assembly consists of the following four values:
@@ -31,6 +31,6 @@ internal static class VersionInfo
         ///      Build Number (MMDD)
         ///      Revision (if any on the same day)
         /// </summary>
-        internal const string FileVersion = "2.18.1110.0";
+        internal const string FileVersion = "2.19.0111.0";
     }
 }
\ No newline at end of file
diff --git a/src/WorkflowActivityLibrary/Activities/GenerateUniqueValue.cs b/src/WorkflowActivityLibrary/Activities/GenerateUniqueValue.cs
index 0da9602..5b95946 100644
--- a/src/WorkflowActivityLibrary/Activities/GenerateUniqueValue.cs
+++ b/src/WorkflowActivityLibrary/Activities/GenerateUniqueValue.cs
@@ -207,6 +207,11 @@ public GenerateUniqueValue()
                 {
                     this.maxLoopCount = 512;
                 }
+
+                if (!bool.TryParse(ConfigurationManager.AppSettings["GenerateUniqueValueActivity_OptimizeUniquenessKey"], out this.optimizeUniquenessKey))
+                {
+                    this.optimizeUniquenessKey = false;
+                }
             }
             finally
             {
@@ -519,7 +524,7 @@ private void SetAttributesToReadForConflictResources()
             Logger.Instance.WriteMethodEntry(EventIdentifier.GenerateUniqueValueSetAttributesToReadForConflictResources, "Filter: '{0}'.", this.ConflictFilter);
 
             this.FindConflict.Attributes = null;
-            this.optimizeUniquenessKey = false;
+            ////this.optimizeUniquenessKey = false; // Now this flag can only be set by app.config.
             string filter = this.ConflictFilter;
             try
             {
@@ -533,15 +538,24 @@ private void SetAttributesToReadForConflictResources()
                 while (startIndex != -1)
                 {
                     int endIndex = filter.IndexOf(endToken, startIndex, StringComparison.OrdinalIgnoreCase);
-                    string s = filter.Substring(startIndex + startTokenLength + 1, endIndex - (startIndex + startTokenLength + 1)).Trim(new char[] { ' ', '(', ',' });
-                    attributes.Add(s);
+                    if (endIndex != -1)
+                    {
+                        string s = filter.Substring(startIndex + startTokenLength + 1, endIndex - (startIndex + startTokenLength + 1)).Trim(new char[] { ' ', '(', ',' });
+                        attributes.Add(s);
+                    }
+                    else
+                    {
+                        // just increment - should never be here as now this function should not get called unless this.optimizeUniquenessKey is set true via app.cong. Issue #61
+                        endIndex = startIndex + startTokenLength;
+                    }
+
                     filter = filter.Substring(endIndex);
                     startIndex = filter.IndexOf(startToken, StringComparison.Ordinal);
                 }
 
                 if (attributes.Count > 0)
                 {
-                    this.optimizeUniquenessKey = true;
+                    ////this.optimizeUniquenessKey = true; // Now this flag can only be set by app.config.
                     this.FindConflict.Attributes = attributes.ToArray();
                     Logger.Instance.WriteVerbose(EventIdentifier.GenerateUniqueValueSetAttributesToReadForConflictResources, "Filter: '{0}'. Attributes: '{1}'.", this.ConflictFilter, string.Join(";", attributes.ToArray()));
                 }
@@ -740,8 +754,11 @@ private void Prepare_ExecuteCode(object sender, EventArgs e)
             {
                 // Find the attributes to read on potentially conflicing resources
                 // so that the uniqueness seed can be repositioned instead of simply incremented
-                // when the conflict filter XPath uses a starts-with fuction 
-                this.SetAttributesToReadForConflictResources();
+                // when the conflict filter XPath uses a starts-with fuction
+                if (this.optimizeUniquenessKey)
+                {
+                    this.SetAttributesToReadForConflictResources();
+                }
 
                 // Default the uniqueness key to the specified uniqueness seed,
                 // resolve the first value expression in the list, and use that value to resolve