diff --git a/AssemblyUnhollower/AssemblyUnhollower.csproj b/AssemblyUnhollower/AssemblyUnhollower.csproj
index c0b4574..bb77bcf 100644
--- a/AssemblyUnhollower/AssemblyUnhollower.csproj
+++ b/AssemblyUnhollower/AssemblyUnhollower.csproj
@@ -4,7 +4,7 @@
         <OutputType>Exe</OutputType>
         <TargetFrameworks>net4.7.2;net5.0;netstandard2.1</TargetFrameworks>
         <Nullable>enable</Nullable>
-        <Version>0.4.17.0</Version>
+        <Version>0.4.17.1</Version>
         <LangVersion>latest</LangVersion>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     </PropertyGroup>
diff --git a/AssemblyUnhollower/Utils/UnstripGenerator.cs b/AssemblyUnhollower/Utils/UnstripGenerator.cs
index 615ff62..2176e70 100644
--- a/AssemblyUnhollower/Utils/UnstripGenerator.cs
+++ b/AssemblyUnhollower/Utils/UnstripGenerator.cs
@@ -28,7 +28,7 @@ public static TypeDefinition CreateDelegateTypeForICallMethod(MethodDefinition u
                 invokeMethod.Parameters.Add(new ParameterDefinition("@this", ParameterAttributes.None, imports.IntPtr));
             foreach (var convertedParameter in convertedMethod.Parameters)
                 invokeMethod.Parameters.Add(new ParameterDefinition(convertedParameter.Name,
-                    convertedParameter.Attributes,
+                    convertedParameter.Attributes & ~ParameterAttributes.Optional,
                     convertedParameter.ParameterType.IsValueType ? convertedParameter.ParameterType : imports.IntPtr));
 
             return delegateType;
diff --git a/ReleaseChangelog.md b/ReleaseChangelog.md
index 217c66b..f88d72a 100644
--- a/ReleaseChangelog.md
+++ b/ReleaseChangelog.md
@@ -3,4 +3,5 @@ This is a small feature update. Generated assemblies should be fully compatible
 New features:
  * PDB generator project (not bundled in release zip) - see README
  * New CLI option `--add-prefix-to` to add Il2Cpp prefix to additional assemblies and namespaces to prevent conflicts with managed libs.
+ * 0.4.17.1 - strip Optional attribute off unstripped ICall delegates as Mono crashed on those 
  
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