diff --git a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
index 3a964d636..b35e16220 100644
--- a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
+++ b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
@@ -138,7 +138,9 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (methodDefinition.HasBody) {
 				var ilReader = new ILReader();
 				var function = ilReader.ReadIL(methodDefinition.Body, CancellationToken);
+				function.CheckInvariant();
 				function.Body = function.Body.AcceptVisitor(new TransformingVisitor());
+				function.CheckInvariant();
 				var statementBuilder = new StatementBuilder(method, cecilMapper);
 				var body = statementBuilder.ConvertAsBlock(function.Body);
 				body.AcceptVisitor(new InsertParenthesesVisitor {
diff --git a/ICSharpCode.Decompiler/IL/Instructions.cs b/ICSharpCode.Decompiler/IL/Instructions.cs
index a720a1ee0..9e8e11b31 100644
--- a/ICSharpCode.Decompiler/IL/Instructions.cs
+++ b/ICSharpCode.Decompiler/IL/Instructions.cs
@@ -1113,10 +1113,6 @@ namespace ICSharpCode.Decompiler.IL
 	public sealed partial class Return : ILInstruction
 	{
 		public override StackType ResultType { get { return StackType.Void; } }
-		protected override InstructionFlags ComputeFlags()
-		{
-			return InstructionFlags.MayBranch | InstructionFlags.EndPointUnreachable;
-		}
 		public override T AcceptVisitor<T>(ILVisitor<T> visitor)
 		{
 			return visitor.VisitReturn(this);
diff --git a/ICSharpCode.Decompiler/IL/Instructions.tt b/ICSharpCode.Decompiler/IL/Instructions.tt
index 9bd92569d..08aff0c94 100644
--- a/ICSharpCode.Decompiler/IL/Instructions.tt
+++ b/ICSharpCode.Decompiler/IL/Instructions.tt
@@ -126,7 +126,7 @@
 		new OpCode("localloc", "Allocates space in the stack frame",
 			CustomClassName("LocAlloc"), Unary, ResultType("I"), MayThrow),
 		new OpCode("ret", "Returns from the current method or lambda.",
-			CustomClassName("Return"), CustomConstructor, MayBranch, UnconditionalBranch),
+			CustomClassName("Return"), CustomConstructor, CustomComputeFlags, MayBranch, UnconditionalBranch),
 		new OpCode("shl", "Shift left", BinaryNumeric),
 		new OpCode("shr", "Shift right", BinaryNumeric),
 		
diff --git a/ICSharpCode.Decompiler/IL/Instructions/Branch.cs b/ICSharpCode.Decompiler/IL/Instructions/Branch.cs
index 141a0de3f..b75462f76 100644
--- a/ICSharpCode.Decompiler/IL/Instructions/Branch.cs
+++ b/ICSharpCode.Decompiler/IL/Instructions/Branch.cs
@@ -75,6 +75,14 @@ namespace ICSharpCode.Decompiler.IL
 			get { return targetBlock != null ? targetBlock.Label : CecilExtensions.OffsetToString(TargetILOffset); }
 		}
 		
+		internal override void CheckInvariant()
+		{
+			base.CheckInvariant();
+			if (targetBlock != null) {
+				Debug.Assert(targetBlock.Parent is BlockContainer);
+				Debug.Assert(this.IsDescendantOf(targetBlock.Parent));
+			}
+		}
 		
 		public override void WriteTo(ITextOutput output)
 		{
diff --git a/ICSharpCode.Decompiler/IL/Instructions/ILInstruction.cs b/ICSharpCode.Decompiler/IL/Instructions/ILInstruction.cs
index 9654f9021..45d9d48de 100644
--- a/ICSharpCode.Decompiler/IL/Instructions/ILInstruction.cs
+++ b/ICSharpCode.Decompiler/IL/Instructions/ILInstruction.cs
@@ -53,8 +53,28 @@ namespace ICSharpCode.Decompiler.IL
 		}
 		
 		[Conditional("DEBUG")]
-		internal void CheckInvariant()
+		internal virtual void CheckInvariant()
 		{
+			foreach (var child in Children) {
+				Debug.Assert(child.Parent == this);
+				// if child flags are invalid, parent flags must be too
+				Debug.Assert(child.flags != invalidFlags || this.flags == invalidFlags);
+				Debug.Assert(child.IsConnected == this.IsConnected);
+				child.CheckInvariant();
+			}
+		}
+		
+		/// <summary>
+		/// Gets whether this node is a descendant of <paramref name="possibleAncestor"/>.
+		/// Also returns true if <c>this</c>==<paramref name="possibleAncestor"/>.
+		/// </summary>
+		public bool IsDescendantOf(ILInstruction possibleAncestor)
+		{
+			for (ILInstruction ancestor = this; ancestor != null; ancestor = ancestor.Parent) {
+				if (ancestor == possibleAncestor)
+					return true;
+			}
+			return false;
 		}
 		
 		/// <summary>
diff --git a/ICSharpCode.Decompiler/IL/Instructions/Return.cs b/ICSharpCode.Decompiler/IL/Instructions/Return.cs
index c7886e3c2..1b8b9f912 100644
--- a/ICSharpCode.Decompiler/IL/Instructions/Return.cs
+++ b/ICSharpCode.Decompiler/IL/Instructions/Return.cs
@@ -47,6 +47,15 @@ namespace ICSharpCode.Decompiler.IL
 			this.ReturnValue = argument;
 		}
 		
+		protected override InstructionFlags ComputeFlags()
+		{
+			InstructionFlags flags = InstructionFlags.MayBranch | InstructionFlags.EndPointUnreachable;
+			if (returnValue != null) {
+				flags |= returnValue.Flags;
+			}
+			return flags;
+		}
+		
 		public override void WriteTo(ITextOutput output)
 		{
 			output.Write(OpCode);
diff --git a/ILSpy/Languages/CSharpLanguage.cs b/ILSpy/Languages/CSharpLanguage.cs
index 9a84d78c7..834f09d5f 100644
--- a/ILSpy/Languages/CSharpLanguage.cs
+++ b/ILSpy/Languages/CSharpLanguage.cs
@@ -212,7 +212,6 @@ namespace ICSharpCode.ILSpy
 		{
 			CSharpDecompiler decompiler = new CSharpDecompiler(type.Module);
 			output.WriteLine(decompiler.Decompile(type).ToString());
-			
 //			AstBuilder codeDomBuilder = CreateAstBuilder(options, currentType: type);
 //			codeDomBuilder.AddType(type);
 //			RunTransformsAndGenerateCode(codeDomBuilder, output, options);