diff --git a/src/RoslynContractFix/ContractFix/ContractFix.Vsix/source.extension.vsixmanifest b/src/RoslynContractFix/ContractFix/ContractFix.Vsix/source.extension.vsixmanifest
index 8ce1274..084ce58 100644
--- a/src/RoslynContractFix/ContractFix/ContractFix.Vsix/source.extension.vsixmanifest
+++ b/src/RoslynContractFix/ContractFix/ContractFix.Vsix/source.extension.vsixmanifest
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <PackageManifest Version="2.0.0" xmlns="http://schemas.microsoft.com/developer/vsx-schema/2011" xmlns:d="http://schemas.microsoft.com/developer/vsx-schema-design/2011">
     <Metadata>
-        <Identity Id="ContractFix.ca38bdda-3bf6-437e-823a-d9214656f65f" Version="1.0" Language="en-US" Publisher="Qoollo"/>
+        <Identity Id="ContractFix.ca38bdda-3bf6-437e-823a-d9214656f65f" Version="1.0.1" Language="en-US" Publisher="Qoollo"/>
         <DisplayName>ContractFix</DisplayName>
         <Description xml:space="preserve">CodeContracts remover</Description>
     </Metadata>
diff --git a/src/RoslynContractFix/ContractFix/ContractFix/CodeContractFromBase/CodeContractFromBaseAnalyzer.cs b/src/RoslynContractFix/ContractFix/ContractFix/CodeContractFromBase/CodeContractFromBaseAnalyzer.cs
index c15beb9..24e662c 100644
--- a/src/RoslynContractFix/ContractFix/ContractFix/CodeContractFromBase/CodeContractFromBaseAnalyzer.cs
+++ b/src/RoslynContractFix/ContractFix/ContractFix/CodeContractFromBase/CodeContractFromBaseAnalyzer.cs
@@ -48,7 +48,7 @@ public override void Initialize(AnalysisContext context)
         private static IEnumerable<IMethodSymbol> GetInterfaceImplementation(IMethodSymbol method)
         {
             return method.ContainingType.AllInterfaces.SelectMany(@interface => @interface.GetMembers().OfType<IMethodSymbol>()).
-                Where(interfaceMethod => method.ContainingType.FindImplementationForInterfaceMember(interfaceMethod).Equals(method));
+                Where(interfaceMethod => method.ContainingType.FindImplementationForInterfaceMember(interfaceMethod)?.Equals(method) ?? false);
         }
         private static IEnumerable<IMethodSymbol> GetOverridenMethods(IMethodSymbol method)
         {
diff --git a/src/RoslynContractFix/ContractFix/ContractFix/RequiresGenericToIfThrow/RequiresGenericToIfThrowCodeFixProvider.cs b/src/RoslynContractFix/ContractFix/ContractFix/RequiresGenericToIfThrow/RequiresGenericToIfThrowCodeFixProvider.cs
index a2e9526..016ebe6 100644
--- a/src/RoslynContractFix/ContractFix/ContractFix/RequiresGenericToIfThrow/RequiresGenericToIfThrowCodeFixProvider.cs
+++ b/src/RoslynContractFix/ContractFix/ContractFix/RequiresGenericToIfThrow/RequiresGenericToIfThrowCodeFixProvider.cs
@@ -51,6 +51,17 @@ public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
                 context.Diagnostics);
         }
 
+        private static bool IsComparisonExpr(ExpressionSyntax expr)
+        {
+            var exprKind = expr.Kind();
+            return exprKind == SyntaxKind.NotEqualsExpression ||
+                   exprKind == SyntaxKind.EqualsExpression ||
+                   exprKind == SyntaxKind.GreaterThanExpression ||
+                   exprKind == SyntaxKind.GreaterThanOrEqualExpression ||
+                   exprKind == SyntaxKind.LessThanExpression ||
+                   exprKind == SyntaxKind.LessThanOrEqualExpression;
+        }
+
         private static ExpressionSyntax SmartNotExpression(ExpressionSyntax expr, SyntaxGenerator generator)
         {
             if (expr is BinaryExpressionSyntax binary)
@@ -69,8 +80,17 @@ private static ExpressionSyntax SmartNotExpression(ExpressionSyntax expr, Syntax
                         return (ExpressionSyntax)generator.GreaterThanOrEqualExpression(binary.Left, binary.Right);
                     case SyntaxKind.LessThanOrEqualExpression:
                         return (ExpressionSyntax)generator.GreaterThanExpression(binary.Left, binary.Right);
+                    case SyntaxKind.LogicalOrExpression when IsComparisonExpr(binary.Left) && IsComparisonExpr(binary.Right):
+                        return (ExpressionSyntax)generator.LogicalAndExpression(SmartNotExpression(binary.Left, generator), SmartNotExpression(binary.Right, generator));
+                    case SyntaxKind.LogicalAndExpression when IsComparisonExpr(binary.Left) && IsComparisonExpr(binary.Right):
+                        return (ExpressionSyntax)generator.LogicalOrExpression(SmartNotExpression(binary.Left, generator), SmartNotExpression(binary.Right, generator));
                 }
             }
+            else if (expr is PrefixUnaryExpressionSyntax prefixUnary)
+            {
+                if (prefixUnary.IsKind(SyntaxKind.LogicalNotExpression))
+                    return prefixUnary.Operand;
+            }
 
             return (ExpressionSyntax)generator.LogicalNotExpression(expr);
         }
diff --git a/src/TestSolution/TestProject/Program.cs b/src/TestSolution/TestProject/Program.cs
index 0e4963a..13a3dbc 100644
--- a/src/TestSolution/TestProject/Program.cs
+++ b/src/TestSolution/TestProject/Program.cs
@@ -24,6 +24,7 @@ static void Test(string val)
         static void ContractTest(string val, int data)
         {
             Contract.Requires<ArgumentNullException>(val != null, "aaa" + "ab");
+            Contract.Requires<ArgumentNullException>(!string.IsNullOrEmpty(val));
             Contract.Requires<ArgumentOutOfRangeException>(data >= 0);
             Contract.Requires<ArgumentException>(data != 0 && val != "fff");
             Contract.Requires<InvalidOperationException>(data < 100);