diff --git a/Tests/NTwain.Tests/Data/TWIdentityTest.cs b/Tests/NTwain.Tests/Data/TWIdentityTest.cs
index 55c828c..6d1ffa9 100644
--- a/Tests/NTwain.Tests/Data/TWIdentityTest.cs
+++ b/Tests/NTwain.Tests/Data/TWIdentityTest.cs
@@ -49,5 +49,27 @@ namespace NTwain.Tests.Data
             string badString = new String('a', overLength);
             target.ProductName = badString;
         }
+
+        [TestMethod]
+        public void Setting_and_Unsetting_the_Shared_Flag_Properties_Works()
+        {
+            TWIdentity id = new TWIdentity();
+
+            // these 2 flag properties are store in same int value so needs to test together
+
+            id.DataFunctionalities = DataFunctionalities.App2;
+            id.DataGroup = DataGroups.Audio;
+            Assert.AreEqual(DataFunctionalities.App2, id.DataFunctionalities);
+            Assert.AreEqual(DataGroups.Audio, id.DataGroup);
+
+            // clear needs to be tested 
+            id.DataFunctionalities = DataFunctionalities.None;
+            Assert.AreEqual(DataFunctionalities.None, id.DataFunctionalities);
+            Assert.AreEqual(DataGroups.Audio, id.DataGroup, "Cleared incorrectly.");
+
+            id.DataGroup = DataGroups.None;
+            Assert.AreEqual(DataGroups.None, id.DataGroup);
+        }
+        
     }
 }
diff --git a/src/NTwain/Data/TwainTypesExtended.cs b/src/NTwain/Data/TwainTypesExtended.cs
index 800ac86..0289c99 100644
--- a/src/NTwain/Data/TwainTypesExtended.cs
+++ b/src/NTwain/Data/TwainTypesExtended.cs
@@ -87,7 +87,7 @@ namespace NTwain.Data
             Buffer.BlockCopy(part, 0, array, 2, 2);
 
             var converted = BitConverter.ToUInt32(array, 0);
-            
+
             return new TWOneValue
             {
                 ItemType = ItemType.Fix32,
@@ -1685,7 +1685,7 @@ namespace NTwain.Data
         public DataGroups DataGroup
         {
             get { return (DataGroups)(_supportedGroups & 0xffff); }
-            set { _supportedGroups |= (uint)value; }
+            set { _supportedGroups = ((uint)value & 0xffff) | (0xffff0000 & _supportedGroups); }
         }
 
         /// <summary>
@@ -1710,7 +1710,7 @@ namespace NTwain.Data
         public DataFunctionalities DataFunctionalities
         {
             get { return (DataFunctionalities)(_supportedGroups & 0xffff0000); }
-            set { _supportedGroups |= (uint)value; }
+            set { _supportedGroups = ((uint)value & 0xffff0000) | (0x0000ffff & _supportedGroups); }
         }
 
         /// <summary>