diff --git a/src/Microsoft.AspNetCore.Routing/Internal/LinkGenerationDecisionTree.cs b/src/Microsoft.AspNetCore.Routing/Internal/LinkGenerationDecisionTree.cs
index eb055f7696..6242198a46 100644
--- a/src/Microsoft.AspNetCore.Routing/Internal/LinkGenerationDecisionTree.cs
+++ b/src/Microsoft.AspNetCore.Routing/Internal/LinkGenerationDecisionTree.cs
@@ -15,6 +15,11 @@ namespace Microsoft.AspNetCore.Routing.Internal
     [DebuggerDisplay("{DebuggerDisplayString,nq}")]
     public class LinkGenerationDecisionTree
     {
+        // Fallback value for cases where the ambient values weren't provided.
+        //
+        // This is safe because we don't mutate the route values in here.
+        private static readonly RouteValueDictionary EmptyAmbientValues = new RouteValueDictionary();
+
         private readonly DecisionTreeNode<OutboundMatch> _root;
 
         public LinkGenerationDecisionTree(IReadOnlyList<OutboundMatch> entries)
@@ -30,7 +35,7 @@ namespace Microsoft.AspNetCore.Routing.Internal
             if (_root.Matches.Count > 0 || _root.Criteria.Count > 0)
             {
                 var results = new List<OutboundMatchResult>();
-                Walk(results, values, ambientValues, _root, isFallbackPath: false);
+                Walk(results, values, ambientValues ?? EmptyAmbientValues, _root, isFallbackPath: false);
                 results.Sort(OutboundMatchResultComparer.Instance);
                 return results;
             }
diff --git a/src/Microsoft.AspNetCore.Routing/LinkGeneratorRouteValuesAddressExtensions.cs b/src/Microsoft.AspNetCore.Routing/LinkGeneratorRouteValuesAddressExtensions.cs
index a2bffc01ef..d025679e41 100644
--- a/src/Microsoft.AspNetCore.Routing/LinkGeneratorRouteValuesAddressExtensions.cs
+++ b/src/Microsoft.AspNetCore.Routing/LinkGeneratorRouteValuesAddressExtensions.cs
@@ -135,7 +135,7 @@ namespace Microsoft.AspNetCore.Routing
                 throw new ArgumentNullException(nameof(httpContext));
             }
 
-            var address = CreateAddress(httpContext: null, routeName, values);
+            var address = CreateAddress(httpContext, routeName, values);
             return generator.GetUriByAddress<RouteValuesAddress>(
                 httpContext,
                 address,
diff --git a/test/Microsoft.AspNetCore.Routing.Tests/Internal/LinkGenerationDecisionTreeTest.cs b/test/Microsoft.AspNetCore.Routing.Tests/Internal/LinkGenerationDecisionTreeTest.cs
index f07296faba..94568c2cd8 100644
--- a/test/Microsoft.AspNetCore.Routing.Tests/Internal/LinkGenerationDecisionTreeTest.cs
+++ b/test/Microsoft.AspNetCore.Routing.Tests/Internal/LinkGenerationDecisionTreeTest.cs
@@ -14,6 +14,26 @@ namespace Microsoft.AspNetCore.Routing.Internal.Routing
 {
     public class LinkGenerationDecisionTreeTest
     {
+        [Fact]
+        public void GetMatches_AllowsNullAmbientValues()
+        {
+            // Arrange
+            var entries = new List<OutboundMatch>();
+
+            var entry = CreateMatch(new { });
+            entries.Add(entry);
+
+            var tree = new LinkGenerationDecisionTree(entries);
+
+            var context = CreateContext(new { });
+
+            // Act
+            var matches = tree.GetMatches(context.Values, ambientValues: null);
+
+            // Assert
+            Assert.Same(entry, Assert.Single(matches).Match);
+        }
+
         [Fact]
         public void SelectSingleEntry_NoCriteria()
         {
diff --git a/test/Microsoft.AspNetCore.Routing.Tests/LinkGeneratorRouteValuesAddressExtensionsTest.cs b/test/Microsoft.AspNetCore.Routing.Tests/LinkGeneratorRouteValuesAddressExtensionsTest.cs
index 57874816d6..57f530cdb8 100644
--- a/test/Microsoft.AspNetCore.Routing.Tests/LinkGeneratorRouteValuesAddressExtensionsTest.cs
+++ b/test/Microsoft.AspNetCore.Routing.Tests/LinkGeneratorRouteValuesAddressExtensionsTest.cs
@@ -170,6 +170,38 @@ namespace Microsoft.AspNetCore.Routing
             Assert.Equal("http://example.com/Foo/Bar%3Fencodeme%3F/Home/Index/?query=some%3Fquery#Fragment?", uri);
         }
 
+        [Fact]
+        public void GetUriByRouteValues_WithHttpContext_CanUseAmbientValues()
+        {
+            // Arrange
+            var endpoint1 = EndpointFactory.CreateRouteEndpoint(
+                "Home/Index/{id}",
+                defaults: new { controller = "Home", action = "Index", },
+                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+            var endpoint2 = EndpointFactory.CreateRouteEndpoint(
+                "Home/Index/{id?}",
+                defaults: new { controller = "Home", action = "Index", },
+                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+
+            var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
+
+            var httpContext = CreateHttpContext(new { controller = "Home", });
+            httpContext.Request.Scheme = "http";
+            httpContext.Request.Host = new HostString("example.com");
+            httpContext.Request.PathBase = new PathString("/Foo/Bar?encodeme?");
+
+            // Act
+            var uri = linkGenerator.GetUriByRouteValues(
+                httpContext,
+                routeName: null,
+                values: new RouteValueDictionary(new { action = "Index", query = "some?query" }),
+                fragment: new FragmentString("#Fragment?"),
+                options: new LinkOptions() { AppendTrailingSlash = true, });
+
+            // Assert
+            Assert.Equal("http://example.com/Foo/Bar%3Fencodeme%3F/Home/Index/?query=some%3Fquery#Fragment?", uri);
+        }
+
         [Fact]
         public void GetTemplateByRouteValues_CreatesTemplate()
         {