diff --git a/src/NHibernate/Engine/Query/QueryPlanCache.cs b/src/NHibernate/Engine/Query/QueryPlanCache.cs
index 6a0c0b6a7ee..01849f96e77 100644
--- a/src/NHibernate/Engine/Query/QueryPlanCache.cs
+++ b/src/NHibernate/Engine/Query/QueryPlanCache.cs
@@ -196,20 +196,23 @@ private class HQLQueryPlanKey : IEquatable<HQLQueryPlanKey>, IDeserializationCal
 			// hashcode may vary among processes, they cannot be stored and have to be re-computed after deserialization
 			[NonSerialized]
 			private int? _hashCode;
+
+			private readonly System.Type queryType;
 			private readonly System.Type queryTypeDiscriminator;
 
 			public HQLQueryPlanKey(string query, bool shallow, IDictionary<string, IFilter> enabledFilters)
-				: this(typeof(object), query, shallow, enabledFilters)
+				: this(typeof(object), typeof(object), query, shallow, enabledFilters)
 			{
 			}
 
 			public HQLQueryPlanKey(IQueryExpression queryExpression, bool shallow, IDictionary<string, IFilter> enabledFilters)
-				: this(queryExpression.GetType(), queryExpression.Key, shallow, enabledFilters)
+				: this(queryExpression.Type, queryExpression.GetType(), queryExpression.Key, shallow, enabledFilters)
 			{
 			}
 
-			protected HQLQueryPlanKey(System.Type queryTypeDiscriminator, string query, bool shallow, IDictionary<string, IFilter> enabledFilters)
+			protected HQLQueryPlanKey(System.Type queryType, System.Type queryTypeDiscriminator, string query, bool shallow, IDictionary<string, IFilter> enabledFilters)
 			{
+				this.queryType = queryType;
 				this.queryTypeDiscriminator = queryTypeDiscriminator;
 				this.query = query;
 				this.shallow = shallow;
@@ -255,6 +258,11 @@ public bool Equals(HQLQueryPlanKey that)
 					return false;
 				}
 
+				if (queryType != that.queryType)
+				{
+					return false;
+				}
+
 				if (queryTypeDiscriminator != that.queryTypeDiscriminator)
 				{
 					return false;
@@ -285,6 +293,7 @@ private int GenerateHashCode()
 					var hash = query.GetHashCode();
 					hash = 29 * hash + (shallow ? 1 : 0);
 					hash = 29 * hash + CollectionHelper.GetHashCode(_filterNames);
+					hash = 29 * hash + queryType.GetHashCode();
 					hash = 29 * hash + queryTypeDiscriminator.GetHashCode();
 					return hash;
 				}