diff --git a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
index bd9ecd13e6..81a2b328bc 100644
--- a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
+++ b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
@@ -30,7 +30,6 @@
 using ICSharpCode.Decompiler.CSharp.OutputVisitor;
 using ICSharpCode.Decompiler.CSharp.Resolver;
 using ICSharpCode.Decompiler.CSharp.Syntax;
-using ICSharpCode.Decompiler.CSharp.Syntax.PatternMatching;
 using ICSharpCode.Decompiler.CSharp.Transforms;
 using ICSharpCode.Decompiler.DebugInfo;
 using ICSharpCode.Decompiler.Disassembler;
@@ -1270,9 +1269,9 @@ void FixParameterNames(EntityDeclaration entity)
 			int i = 0;
 			foreach (var parameter in entity.GetChildrenByRole(Roles.Parameter))
 			{
-				if (string.IsNullOrEmpty(parameter.Name) && !parameter.Type.IsArgList())
+				if (string.IsNullOrWhiteSpace(parameter.Name) && !parameter.Type.IsArgList())
 				{
-					// needs to be consistent with logic in ILReader.CreateILVarable(ParameterDefinition)
+					// needs to be consistent with logic in ILReader.CreateILVarable
 					parameter.Name = "P_" + i;
 				}
 				i++;
diff --git a/ICSharpCode.Decompiler/CSharp/CallBuilder.cs b/ICSharpCode.Decompiler/CSharp/CallBuilder.cs
index d256cf6259..d0f4c056c0 100644
--- a/ICSharpCode.Decompiler/CSharp/CallBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/CallBuilder.cs
@@ -26,6 +26,7 @@
 using ICSharpCode.Decompiler.CSharp.Resolver;
 using ICSharpCode.Decompiler.CSharp.Syntax;
 using ICSharpCode.Decompiler.IL;
+using ICSharpCode.Decompiler.IL.Transforms;
 using ICSharpCode.Decompiler.Semantics;
 using ICSharpCode.Decompiler.TypeSystem;
 using ICSharpCode.Decompiler.TypeSystem.Implementation;
@@ -781,7 +782,7 @@ private ArgumentList BuildArgumentList(ExpectedTargetDetails expectedTargetDetai
 						argumentNames = new string[method.Parameters.Count];
 					}
 					parameter = method.Parameters[argumentToParameterMap[i]];
-					if (argumentNames != null)
+					if (argumentNames != null && AssignVariableNames.IsValidName(parameter.Name))
 					{
 						argumentNames[arguments.Count] = parameter.Name;
 					}
diff --git a/ICSharpCode.Decompiler/IL/ILReader.cs b/ICSharpCode.Decompiler/IL/ILReader.cs
index 10046abaff..6bf9b5b5e4 100644
--- a/ICSharpCode.Decompiler/IL/ILReader.cs
+++ b/ICSharpCode.Decompiler/IL/ILReader.cs
@@ -19,7 +19,6 @@
 #nullable enable
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
@@ -334,7 +333,7 @@ ILVariable CreateILVariable(int index, IType parameterType, string name)
 			Debug.Assert(ilVar.StoreCount == 1); // count the initial store when the method is called with an argument
 			if (index < 0)
 				ilVar.Name = "this";
-			else if (string.IsNullOrEmpty(name))
+			else if (string.IsNullOrWhiteSpace(name))
 				ilVar.Name = "P_" + index;
 			else
 				ilVar.Name = name;
diff --git a/ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs b/ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs
index 2fd3f7782d..2832e9e25a 100644
--- a/ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs
+++ b/ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs
@@ -202,7 +202,9 @@ void PerformAssignment(ILFunction function)
 			{
 				switch (v.Kind)
 				{
-					case VariableKind.Parameter: // ignore
+					case VariableKind.Parameter:
+						// Parameter names are handled in ILReader.CreateILVariable
+						// and CSharpDecompiler.FixParameterNames
 						break;
 					case VariableKind.InitializerTarget: // keep generated names
 						AddExistingName(reservedVariableNames, v.Name);
@@ -326,9 +328,9 @@ bool ConflictWithLocal(ILVariable v)
 			return false;
 		}
 
-		static bool IsValidName(string varName)
+		internal static bool IsValidName(string varName)
 		{
-			if (string.IsNullOrEmpty(varName))
+			if (string.IsNullOrWhiteSpace(varName))
 				return false;
 			if (!(char.IsLetter(varName[0]) || varName[0] == '_'))
 				return false;