diff --git a/ICSharpCode.NRefactory/TypeSystem/IAttribute.cs b/ICSharpCode.NRefactory/TypeSystem/IAttribute.cs
index 26425e2f43..184de64784 100644
--- a/ICSharpCode.NRefactory/TypeSystem/IAttribute.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/IAttribute.cs
@@ -26,9 +26,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 	/// <summary>
 	/// Represents an unresolved attribute.
 	/// </summary>
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(IUnresolvedAttributeContract))]
-	#endif
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
 	public interface IUnresolvedAttribute
 	{
@@ -37,8 +34,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		DomRegion Region { get; }
 		
-		//ITypeReference AttributeType { get; }
-		
 		/// <summary>
 		/// Resolves the attribute.
 		/// </summary>
@@ -48,9 +43,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 	/// <summary>
 	/// Represents an attribute.
 	/// </summary>
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(IAttributeContract))]
-	#endif
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
 	public interface IAttribute
 	{
@@ -80,41 +72,4 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		IList<KeyValuePair<IMember, ResolveResult>> NamedArguments { get; }
 	}
-	
-	#if WITH_CONTRACTS
-	[ContractClassFor(typeof(IAttribute))]
-	abstract class IAttributeContract : IFreezableContract, IAttribute
-	{
-		DomRegion IAttribute.Region {
-			get { return DomRegion.Empty; }
-		}
-		
-		ITypeReference IAttribute.AttributeType {
-			get {
-				Contract.Ensures(Contract.Result<ITypeReference>() != null);
-				return null;
-			}
-		}
-		
-		IList<IConstantValue> IAttribute.GetPositionalArguments(ITypeResolveContext context)
-		{
-			Contract.Requires(context != null);
-			Contract.Ensures(Contract.Result<IList<IConstantValue>>() != null);
-			return null;
-		}
-		
-		IList<KeyValuePair<string, IConstantValue>> IAttribute.GetNamedArguments(ITypeResolveContext context)
-		{
-			Contract.Requires(context != null);
-			Contract.Ensures(Contract.Result<IList<KeyValuePair<string, IConstantValue>>>() != null);
-			return null;
-		}
-		
-		IMethod IAttribute.ResolveConstructor(ITypeResolveContext context)
-		{
-			Contract.Requires(context != null);
-			return null;
-		}
-	}
-	#endif
 }
diff --git a/ICSharpCode.NRefactory/TypeSystem/IFreezable.cs b/ICSharpCode.NRefactory/TypeSystem/IFreezable.cs
index e0b63a28ad..050d09e099 100644
--- a/ICSharpCode.NRefactory/TypeSystem/IFreezable.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/IFreezable.cs
@@ -17,13 +17,9 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
-using System.Diagnostics.Contracts;
 
 namespace ICSharpCode.NRefactory.TypeSystem
 {
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(IFreezableContract))]
-	#endif
 	public interface IFreezable
 	{
 		/// <summary>
@@ -36,20 +32,4 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		void Freeze();
 	}
-	
-	#if WITH_CONTRACTS
-	[ContractClassFor(typeof(IFreezable))]
-	abstract class IFreezableContract : IFreezable
-	{
-		bool IFreezable.IsFrozen {
-			get { return default(bool); }
-		}
-		
-		void IFreezable.Freeze()
-		{
-			IFreezable self = this;
-			Contract.Ensures(self.IsFrozen);
-		}
-	}
-	#endif
 }
diff --git a/ICSharpCode.NRefactory/TypeSystem/IInterningProvider.cs b/ICSharpCode.NRefactory/TypeSystem/IInterningProvider.cs
index dc20e18ef8..89edd7f9f4 100644
--- a/ICSharpCode.NRefactory/TypeSystem/IInterningProvider.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/IInterningProvider.cs
@@ -18,7 +18,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.Contracts;
 
 namespace ICSharpCode.NRefactory.TypeSystem
 {
@@ -40,9 +39,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 	/// and which are used only within a single type definition. Then a persistent file format could be organized so
 	/// that shared objects are loaded only once, yet non-shared objects get loaded lazily together with the class.
 	/// </remarks>
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(IInterningProviderContract))]
-	#endif
 	public interface IInterningProvider
 	{
 		/// <summary>
@@ -55,22 +51,4 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		
 		IList<T> InternList<T>(IList<T> list) where T : class;
 	}
-	
-	#if WITH_CONTRACTS
-	[ContractClassFor(typeof(IInterningProvider))]
-	abstract class IInterningProviderContract : IInterningProvider
-	{
-		T IInterningProvider.Intern<T>(T obj)
-		{
-			Contract.Ensures((Contract.Result<T>() == null) == (obj == null));
-			return obj;
-		}
-		
-		IList<T> IInterningProvider.InternList<T>(IList<T> list)
-		{
-			Contract.Ensures((Contract.Result<IList<T>>() == null) == (list == null));
-			return list;
-		}
-	}
-	#endif
 }
diff --git a/ICSharpCode.NRefactory/TypeSystem/ISupportsInterning.cs b/ICSharpCode.NRefactory/TypeSystem/ISupportsInterning.cs
index 43573ade47..0832e33e90 100644
--- a/ICSharpCode.NRefactory/TypeSystem/ISupportsInterning.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/ISupportsInterning.cs
@@ -17,8 +17,6 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
-using System.Collections.Generic;
-using System.Diagnostics.Contracts;
 
 namespace ICSharpCode.NRefactory.TypeSystem
 {
@@ -26,9 +24,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 	/// Interface for TypeSystem objects that support interning.
 	/// See <see cref="IInterningProvider"/> for more information.
 	/// </summary>
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(ISupportsInterningContract))]
-	#endif
 	public interface ISupportsInterning
 	{
 		/// <summary>
@@ -46,25 +41,4 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		bool EqualsForInterning(ISupportsInterning other);
 	}
-	
-	#if WITH_CONTRACTS
-	[ContractClassFor(typeof(ISupportsInterning))]
-	abstract class ISupportsInterningContract : ISupportsInterning
-	{
-		void ISupportsInterning.PrepareForInterning(IInterningProvider provider)
-		{
-			Contract.Requires(provider != null);
-		}
-		
-		int ISupportsInterning.GetHashCodeForInterning()
-		{
-			return 0;
-		}
-		
-		bool ISupportsInterning.EqualsForInterning(ISupportsInterning other)
-		{
-			return false;
-		}
-	}
-	#endif
 }
diff --git a/ICSharpCode.NRefactory/TypeSystem/ITypeReference.cs b/ICSharpCode.NRefactory/TypeSystem/ITypeReference.cs
index efad8e983c..fc22826c37 100644
--- a/ICSharpCode.NRefactory/TypeSystem/ITypeReference.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/ITypeReference.cs
@@ -17,8 +17,6 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
-using System.Collections.Generic;
-using System.Diagnostics.Contracts;
 
 namespace ICSharpCode.NRefactory.TypeSystem
 {
@@ -26,9 +24,6 @@ namespace ICSharpCode.NRefactory.TypeSystem
 	/// Represents a reference to a type.
 	/// Must be resolved before it can be used as type.
 	/// </summary>
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(ITypeReferenceContract))]
-	#endif
 	public interface ITypeReference
 	{
 		// Keep this interface simple: I decided against having GetMethods/GetEvents etc. here,
@@ -81,17 +76,4 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		ITypeResolveContext WithCurrentTypeDefinition(ITypeDefinition typeDefinition);
 		ITypeResolveContext WithCurrentMember(IMember member);
 	}
-	
-	#if WITH_CONTRACTS
-	[ContractClassFor(typeof(ITypeReference))]
-	abstract class ITypeReferenceContract : ITypeReference
-	{
-		IType ITypeReference.Resolve(ITypeResolveContext context)
-		{
-			Contract.Requires(context != null);
-			Contract.Ensures(Contract.Result<IType>() != null);
-			return null;
-		}
-	}
-	#endif
 }
\ No newline at end of file
diff --git a/ICSharpCode.NRefactory/TypeSystem/IVariable.cs b/ICSharpCode.NRefactory/TypeSystem/IVariable.cs
index e185247707..9e4d45835e 100644
--- a/ICSharpCode.NRefactory/TypeSystem/IVariable.cs
+++ b/ICSharpCode.NRefactory/TypeSystem/IVariable.cs
@@ -17,16 +17,12 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
-using System.Diagnostics.Contracts;
 
 namespace ICSharpCode.NRefactory.TypeSystem
 {
 	/// <summary>
 	/// Represents a variable (name/type pair).
 	/// </summary>
-	#if WITH_CONTRACTS
-	[ContractClass(typeof(IVariableContract))]
-	#endif
 	public interface IVariable
 	{
 		/// <summary>
@@ -55,36 +51,4 @@ namespace ICSharpCode.NRefactory.TypeSystem
 		/// </summary>
 		object ConstantValue { get; }
 	}
-	
-	#if WITH_CONTRACTS
-	[ContractClassFor(typeof(IVariable))]
-	abstract class IVariableContract : IVariable
-	{
-		string IVariable.Name {
-			get {
-				Contract.Ensures(Contract.Result<string>() != null);
-				return null;
-			}
-		}
-		
-		ITypeReference IVariable.Type {
-			get {
-				Contract.Ensures(Contract.Result<ITypeReference>() != null);
-				return null;
-			}
-		}
-		
-		bool IVariable.IsConst {
-			get {
-				IVariable @this = this;
-				Contract.Ensures(Contract.Result<bool>() == (@this.ConstantValue != null));
-				return false;
-			}
-		}
-		
-		object IVariable.ConstantValue {
-			get { return null; }
-		}
-	}
-	#endif
 }