diff --git a/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs b/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs
index 59c10d8d3f896..643856b5ad493 100644
--- a/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs
+++ b/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs
@@ -603,7 +603,8 @@ private static void GetExportedTypes(NamespaceOrTypeSymbol symbol, int parentInd
             foreach (var member in symbol.GetMembers())
             {
                 var namespaceOrType = member as NamespaceOrTypeSymbol;
-                if ((object)namespaceOrType != null)
+                if ((object)namespaceOrType != null &&
+                    member is not NamedTypeSymbol { IsExtension: true }) // https://github.com/dotnet/roslyn/issues/78963 - This is a temporary handling, we should get grouping and marker types processed instead.
                 {
                     GetExportedTypes(namespaceOrType, index, builder);
                 }
@@ -792,6 +793,11 @@ private static void GetForwardedTypes(
                             ImmutableArray<NamedTypeSymbol> nested = type.GetTypeMembers(); // Ordered.
                             for (int i = nested.Length - 1; i >= 0; i--)
                             {
+                                if (nested[i].IsExtension)
+                                {
+                                    continue; // https://github.com/dotnet/roslyn/issues/78963 - This is a temporary handling, we should get grouping and marker types processed instead.
+                                }
+
                                 stack.Push((nested[i], index));
                             }
                         }
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/Metadata/PE/TypeForwarders.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/Metadata/PE/TypeForwarders.cs
index 7396ff9004b6d..54dc455d3aeb0 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/Metadata/PE/TypeForwarders.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/Metadata/PE/TypeForwarders.cs
@@ -1353,6 +1353,29 @@ public class Inner
             CheckForwarderEmit(source1, source2, "NS.Forwarded", "NS.Forwarded+Inner");
         }
 
+        [ClrOnlyFact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/79894")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/78963")]
+        public void Extensions_01()
+        {
+            var source1 = @"
+public static class Extensions
+{
+    extension(int)
+    {
+    }
+}";
+
+            var source2 = @"
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(Extensions))]
+";
+
+            // https://github.com/dotnet/roslyn/issues/78963 - The grouping and marker types should be among the forwarded types since they are public.
+            //                                                 They also should be among exported types for library built from source1. Type symbols
+            //                                                 representing extensions from the language perspective should not be in either set.
+            CheckForwarderEmit(source1, source2, "Extensions");
+        }
+
         [ClrOnlyFact]
         public void EmitForwarder_Nested_Private()
         {