diff --git a/src/vswhere.lib/InstanceSelector.cpp b/src/vswhere.lib/InstanceSelector.cpp
index 9c7db44..7437206 100644
--- a/src/vswhere.lib/InstanceSelector.cpp
+++ b/src/vswhere.lib/InstanceSelector.cpp
@@ -89,29 +89,30 @@ bool InstanceSelector::Less(const ISetupInstancePtr& a, const ISetupInstancePtr&
     }
 }
 
-vector<ISetupInstancePtr> InstanceSelector::Select(_In_ IEnumSetupInstances* pEnum) const
+vector<ISetupInstancePtr> InstanceSelector::Select(_In_opt_ IEnumSetupInstances* pEnum) const
 {
-    _ASSERT(pEnum);
-
-    HRESULT hr = S_OK;
-    unsigned long celtFetched = 0;
-    ISetupInstance* pInstances[1] = {};
-
     vector<ISetupInstancePtr> instances;
-    do
+    if (pEnum)
     {
-        celtFetched = 0;
+        HRESULT hr = S_OK;
+        unsigned long celtFetched = 0;
+        ISetupInstance* pInstances[1] = {};
 
-        hr = pEnum->Next(1, pInstances, &celtFetched);
-        if (SUCCEEDED(hr) && celtFetched)
+        do
         {
-            ISetupInstancePtr instance(pInstances[0], false);
-            if (IsMatch(instance))
+            celtFetched = 0;
+
+            hr = pEnum->Next(1, pInstances, &celtFetched);
+            if (SUCCEEDED(hr) && celtFetched)
             {
-                instances.push_back(instance);
+                ISetupInstancePtr instance(pInstances[0], false);
+                if (IsMatch(instance))
+                {
+                    instances.push_back(instance);
+                }
             }
-        }
-    } while (SUCCEEDED(hr) && celtFetched);
+        } while (SUCCEEDED(hr) && celtFetched);
+    }
 
     if (m_args.get_Latest() && 1 < instances.size())
     {
diff --git a/src/vswhere.lib/InstanceSelector.h b/src/vswhere.lib/InstanceSelector.h
index 1ab701b..b3d601c 100644
--- a/src/vswhere.lib/InstanceSelector.h
+++ b/src/vswhere.lib/InstanceSelector.h
@@ -18,7 +18,7 @@ class InstanceSelector
     }
 
     bool Less(const ISetupInstancePtr& a, const ISetupInstancePtr&  b) const;
-    std::vector<ISetupInstancePtr> Select(_In_ IEnumSetupInstances* pEnum) const;
+    std::vector<ISetupInstancePtr> Select(_In_opt_ IEnumSetupInstances* pEnum) const;
 
 private:
     static std::wstring GetId(_In_ ISetupPackageReference* pPackageReference);
diff --git a/src/vswhere/Program.cpp b/src/vswhere/Program.cpp
index ca7fc3c..9101967 100644
--- a/src/vswhere/Program.cpp
+++ b/src/vswhere/Program.cpp
@@ -7,6 +7,7 @@
 
 using namespace std;
 
+void GetEnumerator(_In_ const CommandArgs& args, _In_ ISetupConfigurationPtr& query, _In_ IEnumSetupInstancesPtr& e);
 void WriteLogo(_In_ const CommandArgs& args, _In_ wostream& out);
 
 int wmain(_In_ int argc, _In_ LPCWSTR argv[])
@@ -30,44 +31,14 @@ int wmain(_In_ int argc, _In_ LPCWSTR argv[])
         ISetupConfigurationPtr query;
         IEnumSetupInstancesPtr e;
 
-        auto hr = query.CreateInstance(__uuidof(SetupConfiguration));
-        if (FAILED(hr))
-        {
-            if (REGDB_E_CLASSNOTREG == hr)
-            {
-                WriteLogo(args, out);
-                return ERROR_SUCCESS;
-            }
-        }
-
-        // If all instances are requested, try to get the proper enumerator; otherwise, fall back to original enumerator.
-        if (args.get_All())
-        {
-            ISetupConfiguration2Ptr query2;
-
-            hr = query->QueryInterface(&query2);
-            if (SUCCEEDED(hr))
-            {
-                hr = query2->EnumAllInstances(&e);
-                if (FAILED(hr))
-                {
-                    throw win32_error(hr);
-                }
-            }
-        }
-
-        if (!e)
-        {
-            hr = query->EnumInstances(&e);
-            if (FAILED(hr))
-            {
-                throw win32_error(hr);
-            }
-        }
+        GetEnumerator(args, query, e);
 
         // Attempt to get the ISetupHelper.
         ISetupHelperPtr helper;
-        query->QueryInterface(&helper);
+        if (query)
+        {
+            query->QueryInterface(&helper);
+        }
 
         InstanceSelector selector(args, helper);
         auto instances = selector.Select(e);
@@ -99,6 +70,45 @@ int wmain(_In_ int argc, _In_ LPCWSTR argv[])
     return E_FAIL;
 }
 
+void GetEnumerator(_In_ const CommandArgs& args, _In_ ISetupConfigurationPtr& query, _In_ IEnumSetupInstancesPtr& e)
+{
+    auto hr = query.CreateInstance(__uuidof(SetupConfiguration));
+    if (FAILED(hr))
+    {
+        if (REGDB_E_CLASSNOTREG == hr)
+        {
+            return;
+        }
+
+        throw win32_error(hr);
+    }
+
+    // If all instances are requested, try to get the proper enumerator; otherwise, fall back to original enumerator.
+    if (args.get_All())
+    {
+        ISetupConfiguration2Ptr query2;
+
+        hr = query->QueryInterface(&query2);
+        if (SUCCEEDED(hr))
+        {
+            hr = query2->EnumAllInstances(&e);
+            if (FAILED(hr))
+            {
+                throw win32_error(hr);
+            }
+        }
+    }
+
+    if (!e)
+    {
+        hr = query->EnumInstances(&e);
+        if (FAILED(hr))
+        {
+            throw win32_error(hr);
+        }
+    }
+}
+
 void WriteLogo(_In_ const CommandArgs& args, _In_ wostream& out)
 {
     if (args.get_Logo())
diff --git a/test/vswhere.test/InstanceSelectorTests.cpp b/test/vswhere.test/InstanceSelectorTests.cpp
index 6914dda..1bebe6c 100644
--- a/test/vswhere.test/InstanceSelectorTests.cpp
+++ b/test/vswhere.test/InstanceSelectorTests.cpp
@@ -11,6 +11,17 @@ using namespace Microsoft::VisualStudio::CppUnitTestFramework;
 TEST_CLASS(InstanceSelectorTests)
 {
 public:
+    TEST_METHOD(Select_Null)
+    {
+        CommandArgs args;
+        args.Parse(L"vswhere.exe");
+
+        InstanceSelector sut(args);
+        auto selected = sut.Select(NULL);
+
+        Assert::AreEqual<size_t>(0, selected.size());
+    }
+
     TEST_METHOD(Select_No_Product)
     {
         TestInstance instance =