diff --git a/src/StreamJsonRpc/Reflection/ProxyBase.cs b/src/StreamJsonRpc/Reflection/ProxyBase.cs
index 393aa37a..0d188d88 100644
--- a/src/StreamJsonRpc/Reflection/ProxyBase.cs
+++ b/src/StreamJsonRpc/Reflection/ProxyBase.cs
@@ -381,22 +381,17 @@ private static bool ProxyImplementsCompatibleSetOfInterfaces(
         JsonRpcProxyOptions? options)
     {
         HashSet<Type> proxyInterfaces = [.. proxyClass.GetInterfaces()];
-        if (!proxyInterfaces.Remove(contractInterface))
-        {
-            return false;
-        }
 
-        foreach (Type addl in additionalContractInterfaces)
+        // Put all the interfaces required into a set so that duplicates are removed.
+        HashSet<Type> requiredInterfaces = [contractInterface, .. additionalContractInterfaces];
+        foreach ((Type addl, _) in implementedOptionalInterfaces)
         {
-            if (!proxyInterfaces.Remove(addl))
-            {
-                return false;
-            }
+            requiredInterfaces.Add(addl);
         }
 
-        foreach ((Type addl, _) in implementedOptionalInterfaces)
+        foreach (Type reqd in requiredInterfaces)
         {
-            if (!proxyInterfaces.Remove(addl))
+            if (!proxyInterfaces.Remove(reqd))
             {
                 return false;
             }
@@ -421,22 +416,35 @@ private static bool ProxyImplementsCompatibleSetOfInterfaces(
                 continue;
             }
 
+            bool ok = false;
             foreach (Type addl in additionalContractInterfaces)
             {
                 if (remaining.IsAssignableFrom(addl))
                 {
+                    ok = true;
                     continue;
                 }
             }
 
+            if (ok)
+            {
+                continue;
+            }
+
             foreach ((Type addl, _) in implementedOptionalInterfaces)
             {
                 if (remaining.IsAssignableFrom(addl))
                 {
+                    ok = true;
                     continue;
                 }
             }
 
+            if (ok)
+            {
+                continue;
+            }
+
             // This is an extra, unwanted interface.
             return false;
         }
diff --git a/src/StreamJsonRpc/Reflection/ProxyInputs.cs b/src/StreamJsonRpc/Reflection/ProxyInputs.cs
index bda0211d..be98bad3 100644
--- a/src/StreamJsonRpc/Reflection/ProxyInputs.cs
+++ b/src/StreamJsonRpc/Reflection/ProxyInputs.cs
@@ -67,7 +67,7 @@ internal ProxyInputs(ProxyInputs copyFrom)
     /// <summary>
     /// Gets a description of the requirements on the proxy to be used.
     /// </summary>
-    internal string Requirements => $"Implementing interface(s): {string.Join(", ", [this.ContractInterface, .. this.AdditionalContractInterfaces.Span])}.";
+    internal string Requirements => $"Implementing interface(s): {string.Join(", ", [this.ContractInterface, .. this.AdditionalContractInterfaces.Span])}";
 
     /// <summary>
     /// Sorts <paramref name="list"/> so that:
diff --git a/test/StreamJsonRpc.Tests/JsonRpcProxyGenerationTests.cs b/test/StreamJsonRpc.Tests/JsonRpcProxyGenerationTests.cs
index e12857aa..511085dc 100644
--- a/test/StreamJsonRpc.Tests/JsonRpcProxyGenerationTests.cs
+++ b/test/StreamJsonRpc.Tests/JsonRpcProxyGenerationTests.cs
@@ -997,9 +997,11 @@ private static void DynamicAssembliesKeyedByAssemblyLoadContext_Helper(JsonRpcPr
 
 #if NO_INTERCEPTORS
     public class Dynamic(ITestOutputHelper logger) : JsonRpcProxyGenerationTests(logger, JsonRpcProxyOptions.ProxyImplementation.AlwaysDynamic);
-#else
+#endif
+
     public class SourceGenerated(ITestOutputHelper logger) : JsonRpcProxyGenerationTests(logger, JsonRpcProxyOptions.ProxyImplementation.AlwaysSourceGenerated)
     {
+#if !NO_INTERCEPTORS
         /// <summary>
         /// The interceptor cannot fallback to dynamic proxies at runtime when the Options demands it,
         /// because doing so would generate linker warnings for NativeAOT apps.
@@ -1066,9 +1068,8 @@ public async Task CheckedInProxiesFromPastGenerationsStillWork()
 
             Assert.Equal(0, failures);
         }
-    }
-
 #endif
+    }
 
     public class EmptyClass
     {