diff --git a/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs b/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs
index 2ca4150db5114..35b2bc58b3301 100644
--- a/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs
+++ b/src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs
@@ -1667,7 +1667,7 @@ private ImmutableArray<ISymbol> LookupSymbolsInternal(
                     TypeSymbol containingType = (TypeSymbol)container;
                     foreach (MethodSymbol extensionMethod in lookupResult.Symbols)
                     {
-                        var reduced = extensionMethod.ReduceExtensionMethod(containingType, Compilation);
+                        var reduced = extensionMethod.ReduceExtensionMethod(containingType, Compilation, discardUseSiteInfo: true);
                         if ((object)reduced != null)
                         {
                             results.Add(reduced.GetPublicSymbol());
diff --git a/src/Compilers/CSharp/Portable/Symbols/MethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/MethodSymbol.cs
index e359a98d68fa7..0db6182230402 100644
--- a/src/Compilers/CSharp/Portable/Symbols/MethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/MethodSymbol.cs
@@ -738,7 +738,7 @@ public override TResult Accept<TResult>(CSharpSymbolVisitor<TResult> visitor)
         /// <param name="compilation">The compilation in which constraints should be checked.
         /// Should not be null, but if it is null we treat constraints as we would in the latest
         /// language version.</param>
-        public MethodSymbol ReduceExtensionMethod(TypeSymbol receiverType, CSharpCompilation compilation)
+        public MethodSymbol ReduceExtensionMethod(TypeSymbol receiverType, CSharpCompilation compilation, bool discardUseSiteInfo = false)
         {
             if ((object)receiverType == null)
             {
@@ -750,7 +750,7 @@ public MethodSymbol ReduceExtensionMethod(TypeSymbol receiverType, CSharpCompila
                 return null;
             }
 
-            return ReducedExtensionMethodSymbol.Create(this, receiverType, compilation);
+            return ReducedExtensionMethodSymbol.Create(this, receiverType, compilation, discardUseSiteInfo);
         }
 
         /// <summary>
diff --git a/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs
index c59e90fd57611..ee6faafc48719 100644
--- a/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs
@@ -34,13 +34,15 @@ internal sealed class ReducedExtensionMethodSymbol : MethodSymbol
         /// </summary>
         /// <param name="compilation">Compilation used to check constraints.
         /// The latest language version is assumed if this is null.</param>
-        public static MethodSymbol Create(MethodSymbol method, TypeSymbol receiverType, CSharpCompilation compilation)
+        public static MethodSymbol Create(MethodSymbol method, TypeSymbol receiverType, CSharpCompilation compilation, bool discardUseSiteInfo = false)
         {
             Debug.Assert(method.IsExtensionMethod && method.MethodKind != MethodKind.ReducedExtension);
             Debug.Assert(method.ParameterCount > 0);
             Debug.Assert((object)receiverType != null);
 
-            var useSiteInfo = CompoundUseSiteInfo<AssemblySymbol>.DiscardedDependencies;
+            var useSiteInfo = discardUseSiteInfo
+                ? CompoundUseSiteInfo<AssemblySymbol>.Discarded
+                : CompoundUseSiteInfo<AssemblySymbol>.DiscardedDependencies;
 
             method = InferExtensionMethodTypeArguments(method, receiverType, compilation, ref useSiteInfo);
             if ((object)method == null)
@@ -55,7 +57,7 @@ public static MethodSymbol Create(MethodSymbol method, TypeSymbol receiverType,
                 return null;
             }
 
-            if (useSiteInfo.Diagnostics != null)
+            if (!discardUseSiteInfo && useSiteInfo.Diagnostics != null)
             {
                 foreach (var diag in useSiteInfo.Diagnostics)
                 {