diff --git a/src/Microsoft.VisualStudio.LanguageServices.Razor/DefaultTagHelperFactsService.cs b/src/Microsoft.VisualStudio.LanguageServices.Razor/DefaultTagHelperFactsService.cs
index 30e2c381af..ea6224cac3 100644
--- a/src/Microsoft.VisualStudio.LanguageServices.Razor/DefaultTagHelperFactsService.cs
+++ b/src/Microsoft.VisualStudio.LanguageServices.Razor/DefaultTagHelperFactsService.cs
@@ -138,11 +138,6 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
                 throw new ArgumentNullException(nameof(documentContext));
             }
 
-            if (parentTag == null)
-            {
-                throw new ArgumentNullException(nameof(parentTag));
-            }
-
             var matchingDescriptors = new List<TagHelperDescriptor>();
             var descriptors = documentContext?.TagHelpers;
             if (descriptors?.Count == 0)
diff --git a/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultTagHelperFactsServiceTest.cs b/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultTagHelperFactsServiceTest.cs
index 90f0df6420..d7336c9965 100644
--- a/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultTagHelperFactsServiceTest.cs
+++ b/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultTagHelperFactsServiceTest.cs
@@ -286,6 +286,26 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
             Assert.Equal(expectedDescriptors, descriptors, TagHelperDescriptorComparer.CaseSensitive);
         }
 
+        [Fact]
+        public void GetTagHelpersGivenParent_AllowsRootParentTag()
+        {
+            // Arrange
+            var documentDescriptors = new[]
+            {
+                ITagHelperDescriptorBuilder.Create("TestType", "TestAssembly")
+                    .TagMatchingRule(rule => rule.RequireTagName("div"))
+                    .Build()
+            };
+            var documentContext = TagHelperDocumentContext.Create(string.Empty, documentDescriptors);
+            var service = new DefaultTagHelperFactsService();
+
+            // Act
+            var descriptors = service.GetTagHelpersGivenParent(documentContext, parentTag: null /* root */);
+
+            // Assert
+            Assert.Equal(documentDescriptors, descriptors, TagHelperDescriptorComparer.CaseSensitive);
+        }
+
         [Fact]
         public void GetTagHelpersGivenParent_AllowsUnspecifiedParentTagHelpers()
         {