diff --git a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
index 24361c55c829e..99ba0bf213b20 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
+++ b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
@@ -838,17 +838,22 @@ internal Type[] GetPopulatedTypes(Module module)
         {
             List<Type> typeList = new List<Type>();
 
-            // Manual use of IDictionaryEnumerator instead of foreach to avoid DictionaryEntry box allocations.
-            IDictionaryEnumerator e = _typeData.GetEnumerator();
-            while (e.MoveNext())
+            lock (s_internalSyncObject)
             {
-                DictionaryEntry de = e.Entry;
-                Type type = (Type)de.Key;
-                ReflectedTypeData typeData = (ReflectedTypeData)de.Value;
-
-                if (type.Module == module && typeData.IsPopulated)
+                Hashtable typeData = _typeData;
+                if (typeData != null)
                 {
-                    typeList.Add(type);
+                    // Manual use of IDictionaryEnumerator instead of foreach to avoid DictionaryEntry box allocations.
+                    IDictionaryEnumerator e = typeData.GetEnumerator();
+                    while (e.MoveNext())
+                    {
+                        DictionaryEntry de = e.Entry;
+                        Type type = (Type)de.Key;
+                        if (type.Module == module && ((ReflectedTypeData)de.Value).IsPopulated)
+                        {
+                            typeList.Add(type);
+                        }
+                    }
                 }
             }