diff --git a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingParameterSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingParameterSymbol.cs
index dd32f3e7212af..d2c1941eba75a 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingParameterSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingParameterSymbol.cs
@@ -5,7 +5,9 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
+using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Emit;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.Symbols.Retargeting
 {
@@ -23,6 +25,8 @@ internal abstract class RetargetingParameterSymbol : WrappedParameterSymbol
         /// </summary>
         private ImmutableArray<CSharpAttributeData> _lazyCustomAttributes;
 
+        private TypeWithAnnotations? _lazyTypeWithAnnotations;
+
         protected RetargetingParameterSymbol(ParameterSymbol underlyingParameter)
             : base(underlyingParameter)
         {
@@ -38,7 +42,12 @@ public sealed override TypeWithAnnotations TypeWithAnnotations
         {
             get
             {
-                return this.RetargetingModule.RetargetingTranslator.Retarget(_underlyingParameter.TypeWithAnnotations, RetargetOptions.RetargetPrimitiveTypesByTypeCode);
+                if (!_lazyTypeWithAnnotations.HasValue)
+                {
+                    _lazyTypeWithAnnotations = this.RetargetingModule.RetargetingTranslator.Retarget(_underlyingParameter.TypeWithAnnotations, RetargetOptions.RetargetPrimitiveTypesByTypeCode);
+                }
+
+                return _lazyTypeWithAnnotations.Value;
             }
         }