diff --git a/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs b/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
index ac6e1c347..938378a19 100644
--- a/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
@@ -81,6 +81,8 @@ namespace ICSharpCode.Decompiler.CSharp
 			{
 				if (Type.IsKnownType(KnownTypeCode.Boolean) || Type.Kind == TypeKind.Unknown)
 					return Expression;
+				else if (Expression is PrimitiveExpression && Type.IsKnownType(KnownTypeCode.Int32))
+					return new PrimitiveExpression((int)((PrimitiveExpression)Expression).Value != 0);
 				else if (Type.Kind == TypeKind.Pointer)
 					return new BinaryOperatorExpression(Expression, BinaryOperatorType.InEquality, new NullReferenceExpression());
 				else
diff --git a/ICSharpCode.Decompiler/CSharp/StatementBuilder.cs b/ICSharpCode.Decompiler/CSharp/StatementBuilder.cs
index cad2e879d..c75d9b2e8 100644
--- a/ICSharpCode.Decompiler/CSharp/StatementBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/StatementBuilder.cs
@@ -58,6 +58,11 @@ namespace ICSharpCode.Decompiler.CSharp
 		{
 			return new EmptyStatement();
 		}
+		
+		protected internal override Statement VisitVoid(ICSharpCode.Decompiler.IL.Void inst)
+		{
+			return new ExpressionStatement(exprBuilder.Convert(inst.Argument));
+		}
 
 		protected internal override Statement VisitIfInstruction(IfInstruction inst)
 		{
diff --git a/ICSharpCode.Decompiler/IL/ILReader.cs b/ICSharpCode.Decompiler/IL/ILReader.cs
index 95953d0a8..ed2024a53 100644
--- a/ICSharpCode.Decompiler/IL/ILReader.cs
+++ b/ICSharpCode.Decompiler/IL/ILReader.cs
@@ -120,6 +120,7 @@ namespace ICSharpCode.Decompiler.IL
 				if (outputStacks != null)
 					outputStacks.Add(start, stack.ToImmutableArray());
 				ILInstruction decodedInstruction = DecodeInstruction();
+				decodedInstruction.CheckInvariant();
 				if (decodedInstruction.ResultType != StackType.Void)
 					stack.Push(decodedInstruction.ResultType);
 				decodedInstruction.ILRange = new Interval(start, reader.Position);
diff --git a/ICSharpCode.Decompiler/IL/ILTypeExtensions.cs b/ICSharpCode.Decompiler/IL/ILTypeExtensions.cs
index bdf1a297d..8340ff320 100644
--- a/ICSharpCode.Decompiler/IL/ILTypeExtensions.cs
+++ b/ICSharpCode.Decompiler/IL/ILTypeExtensions.cs
@@ -45,7 +45,12 @@ namespace ICSharpCode.Decompiler.IL
 
 		public static StackType GetStackType(this TypeReference typeRef)
 		{
-			return typeRef.SkipModifiers().MetadataType.GetStackType();
+			typeRef = typeRef.SkipModifiers();
+			TypeDefinition typeDef = typeRef.Resolve();
+			if (typeDef != null && typeDef.IsEnum) {
+				typeRef = typeDef.GetEnumUnderlyingType();
+			}
+			return typeRef.MetadataType.GetStackType();
 		}
 
 		public static TypeReference SkipModifiers(this TypeReference typeRef)
diff --git a/ICSharpCode.Decompiler/IL/Instructions/IfInstruction.cs b/ICSharpCode.Decompiler/IL/Instructions/IfInstruction.cs
index 3977c5a00..833746d3c 100644
--- a/ICSharpCode.Decompiler/IL/Instructions/IfInstruction.cs
+++ b/ICSharpCode.Decompiler/IL/Instructions/IfInstruction.cs
@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 
 namespace ICSharpCode.Decompiler.IL
 {
@@ -30,6 +31,12 @@ namespace ICSharpCode.Decompiler.IL
 			this.FalseInst = falseInst ?? new Nop();
 		}
 		
+		internal override void CheckInvariant()
+		{
+			base.CheckInvariant();
+			Debug.Assert(condition.ResultType == StackType.I4);
+		}
+		
 		public override StackType ResultType {
 			get {
 				return CommonResultType(trueInst.ResultType, falseInst.ResultType);