diff --git a/ICSharpCode.Decompiler/TypeSystem/IParameter.cs b/ICSharpCode.Decompiler/TypeSystem/IParameter.cs
index 530f2406a..481613318 100644
--- a/ICSharpCode.Decompiler/TypeSystem/IParameter.cs
+++ b/ICSharpCode.Decompiler/TypeSystem/IParameter.cs
@@ -105,44 +105,4 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// </summary>
 		IParameterizedMember? Owner { get; }
 	}
-
-	internal static class IParameterExtensions
-	{
-		/// <summary>
-		/// Checks if the parameter is allowed to be assigned a default value.
-		/// </summary>
-		/// <remarks>
-		/// This checks <see cref="IParameter.IsOptional"/>, <see cref="IParameter.HasConstantValueInSignature"/>, <see cref="IParameter.ReferenceKind"/>,
-		/// and <see cref="IParameter.IsParams"/> on this parameter and all subsequent parameters.
-		/// If the parameter has no <see cref="IParameter.Owner"/>, it does not check subsequent parameters.
-		/// </remarks>
-		/// <param name="parameter">The parameter</param>
-		/// <returns>True if the <paramref name="parameter"/> has a default value and is allowed to be assigned a default value.</returns>
-		public static bool IsDefaultValueAssignmentAllowed(this IParameter parameter)
-		{
-			if (!DefaultValueAssignmentAllowedIndividual(parameter))
-				return false;
-
-			if (parameter.Owner == null)
-				return true;
-
-			for (int i = parameter.Owner.Parameters.Count - 1; i >= 0; i--)
-			{
-				IParameter otherParameter = parameter.Owner.Parameters[i];
-				if (otherParameter == parameter)
-					break;
-
-				if (DefaultValueAssignmentAllowedIndividual(otherParameter) || otherParameter.IsParams)
-					continue;
-
-				return false;
-			}
-			return true;
-
-			static bool DefaultValueAssignmentAllowedIndividual(IParameter parameter)
-			{
-				return parameter.IsOptional && parameter.HasConstantValueInSignature && parameter.ReferenceKind is ReferenceKind.None or ReferenceKind.In or ReferenceKind.RefReadOnly;
-			}
-		}
-	}
 }
diff --git a/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs b/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs
index e26781cfb..8689fc95f 100644
--- a/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs
+++ b/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs
@@ -612,6 +612,45 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		}
 		#endregion
 
+		#region IParameter.IsDefaultValueAssignmentAllowed
+		/// <summary>
+		/// Checks if the parameter is allowed to be assigned a default value.
+		/// </summary>
+		/// <remarks>
+		/// This checks <see cref="IParameter.IsOptional"/>, <see cref="IParameter.HasConstantValueInSignature"/>, <see cref="IParameter.ReferenceKind"/>,
+		/// and <see cref="IParameter.IsParams"/> on this parameter and all subsequent parameters.
+		/// If the parameter has no <see cref="IParameter.Owner"/>, it does not check subsequent parameters.
+		/// </remarks>
+		/// <param name="parameter">The parameter</param>
+		/// <returns>True if the <paramref name="parameter"/> has a default value and is allowed to be assigned a default value.</returns>
+		public static bool IsDefaultValueAssignmentAllowed(this IParameter parameter)
+		{
+			if (!DefaultValueAssignmentAllowedIndividual(parameter))
+				return false;
+
+			if (parameter.Owner == null)
+				return true;
+
+			for (int i = parameter.Owner.Parameters.Count - 1; i >= 0; i--)
+			{
+				IParameter otherParameter = parameter.Owner.Parameters[i];
+				if (otherParameter == parameter)
+					break;
+
+				if (DefaultValueAssignmentAllowedIndividual(otherParameter) || otherParameter.IsParams)
+					continue;
+
+				return false;
+			}
+			return true;
+
+			static bool DefaultValueAssignmentAllowedIndividual(IParameter parameter)
+			{
+				return parameter.IsOptional && parameter.HasConstantValueInSignature && parameter.ReferenceKind is ReferenceKind.None or ReferenceKind.In or ReferenceKind.RefReadOnly;
+			}
+		}
+		#endregion
+
 		#region IAssembly.GetTypeDefinition(string,string,int)
 		/// <summary>
 		/// Gets the type definition for a top-level type.