diff --git a/src/Microsoft.Blazor.Browser.JS/src/GlobalExports.ts b/src/Microsoft.Blazor.Browser.JS/src/GlobalExports.ts
index 88325225b6..2f49ae5e06 100644
--- a/src/Microsoft.Blazor.Browser.JS/src/GlobalExports.ts
+++ b/src/Microsoft.Blazor.Browser.JS/src/GlobalExports.ts
@@ -1,13 +1,11 @@
 import { platform } from './Environment'
 import { registerFunction } from './RegisteredFunction';
 
-// This file defines an export that, when the library is loaded in a browser via a
-// <script> element, will be attached to the global namespace
-const blazorInstance = {
-  platform: platform,
-  registerFunction: registerFunction
-};
-
 if (typeof window !== 'undefined') {
-  window['Blazor'] = blazorInstance;
+  // When the library is loaded in a browser via a <script> element, make the
+  // following APIs available in global scope for invocation from JS
+  window['Blazor'] = {
+    platform,
+    registerFunction,
+  };
 }
diff --git a/src/Microsoft.Blazor.Browser.JS/src/InternalRegisteredFunction.ts b/src/Microsoft.Blazor.Browser.JS/src/InternalRegisteredFunction.ts
new file mode 100644
index 0000000000..84f59f68bb
--- /dev/null
+++ b/src/Microsoft.Blazor.Browser.JS/src/InternalRegisteredFunction.ts
@@ -0,0 +1,12 @@
+import { invokeWithJsonMarshalling } from './RegisteredFunction';
+import { attachComponentToElement, renderRenderTree } from './Rendering/Renderer';
+
+/**
+ * The definitive list of internal functions invokable from .NET code.
+ * These function names are treated as 'reserved' and cannot be passed to registerFunction.
+ */
+export const internalRegisteredFunctions = {
+  attachComponentToElement,
+  invokeWithJsonMarshalling,
+  renderRenderTree,
+};
diff --git a/src/Microsoft.Blazor.Browser.JS/src/Platform/Mono/MonoPlatform.ts b/src/Microsoft.Blazor.Browser.JS/src/Platform/Mono/MonoPlatform.ts
index 1a37ccd00f..3264572e4f 100644
--- a/src/Microsoft.Blazor.Browser.JS/src/Platform/Mono/MonoPlatform.ts
+++ b/src/Microsoft.Blazor.Browser.JS/src/Platform/Mono/MonoPlatform.ts
@@ -1,5 +1,6 @@
 import { MethodHandle, System_Object, System_String, System_Array, Pointer, Platform } from '../Platform';
 import { getAssemblyNameFromUrl } from '../DotNet';
+import { getRegisteredFunction } from '../../RegisteredFunction';
 
 let assembly_load: (assemblyName: string) => number;
 let find_class: (assemblyHandle: number, namespace: string, className: string) => number;
@@ -120,6 +121,10 @@ export const monoPlatform: Platform = {
   },
 };
 
+// Bypass normal type checking to add this extra function. It's only intended to be called from
+// the JS code in Mono's driver.c. It's never intended to be called from TypeScript.
+(monoPlatform as any).monoGetRegisteredFunction = getRegisteredFunction;
+
 function addScriptTagsToDocument() {
   // Load either the wasm or asm.js version of the Mono runtime
   const browserSupportsNativeWebAssembly = typeof WebAssembly !== 'undefined' && WebAssembly.validate;
diff --git a/src/Microsoft.Blazor.Browser.JS/src/RegisteredFunction.ts b/src/Microsoft.Blazor.Browser.JS/src/RegisteredFunction.ts
index ffd6b117d1..2d8da71e20 100644
--- a/src/Microsoft.Blazor.Browser.JS/src/RegisteredFunction.ts
+++ b/src/Microsoft.Blazor.Browser.JS/src/RegisteredFunction.ts
@@ -1,12 +1,14 @@
 import { System_String } from './Platform/Platform';
 import { platform } from './Environment';
+import { internalRegisteredFunctions } from './InternalRegisteredFunction';
 
-const registeredFunctions: { [identifier: string]: Function } = {};
-
-// Code in Mono 'driver.c' looks for the registered functions here
-window['__blazorRegisteredFunctions'] = registeredFunctions;
+const registeredFunctions: { [identifier: string]: Function | undefined } = {};
 
 export function registerFunction(identifier: string, implementation: Function) {
+  if (internalRegisteredFunctions.hasOwnProperty(identifier)) {
+    throw new Error(`The function identifier '${identifier}' is reserved and cannot be registered.`);
+  }
+
   if (registeredFunctions.hasOwnProperty(identifier)) {
     throw new Error(`A function with the identifier '${identifier}' has already been registered.`);
   }
@@ -14,13 +16,19 @@ export function registerFunction(identifier: string, implementation: Function) {
   registeredFunctions[identifier] = implementation;
 }
 
-// Handle the JSON-marshalled RegisteredFunction.Invoke calls
-registerFunction('__blazor_InvokeJson', (identifier: System_String, ...argsJson: System_String[]) => {
-  const identifierJsString = platform.toJavaScriptString(identifier);
-  if (!(registeredFunctions && registeredFunctions.hasOwnProperty(identifierJsString))) {
-    throw new Error(`Could not find registered function with name "${identifierJsString}".`);
+export function getRegisteredFunction(identifier: string): Function {
+  // By prioritising the internal ones, we ensure you can't override them
+  const result = internalRegisteredFunctions[identifier] || registeredFunctions[identifier];
+  if (result) {
+    return result;
+  } else {
+    throw new Error(`Could not find registered function with name '${identifier}'.`);
   }
-  const funcInstance = registeredFunctions[identifierJsString];
+}
+
+export function invokeWithJsonMarshalling(identifier: System_String, ...argsJson: System_String[]) {
+  const identifierJsString = platform.toJavaScriptString(identifier);
+  const funcInstance = getRegisteredFunction(identifierJsString);
   const args = argsJson.map(json => JSON.parse(platform.toJavaScriptString(json)));
   const result = funcInstance.apply(null, args);
   if (result !== null && result !== undefined) {
@@ -29,4 +37,4 @@ registerFunction('__blazor_InvokeJson', (identifier: System_String, ...argsJson:
   } else {
     return null;
   }
-});
+}
diff --git a/src/Microsoft.Blazor.Browser.JS/src/Rendering/Renderer.ts b/src/Microsoft.Blazor.Browser.JS/src/Rendering/Renderer.ts
index 911b573fe9..c331bc7c22 100644
--- a/src/Microsoft.Blazor.Browser.JS/src/Rendering/Renderer.ts
+++ b/src/Microsoft.Blazor.Browser.JS/src/Rendering/Renderer.ts
@@ -1,5 +1,4 @@
-import { registerFunction } from '../RegisteredFunction';
-import { System_Object, System_String, System_Array, MethodHandle, Pointer } from '../Platform/Platform';
+import { System_Object, System_String, System_Array, MethodHandle, Pointer } from '../Platform/Platform';
 import { platform } from '../Environment';
 import { getTreeNodePtr, renderTreeNode, NodeType, RenderTreeNodePointer } from './RenderTreeNode';
 let raiseEventMethod: MethodHandle;
@@ -14,10 +13,7 @@ type ComponentIdToParentElement = { [componentId: number]: Element };
 type BrowserRendererRegistry = { [browserRendererId: number]: ComponentIdToParentElement };
 const browserRenderers: BrowserRendererRegistry = {};
 
-registerFunction('_blazorAttachComponentToElement', attachComponentToElement);
-registerFunction('_blazorRender', renderRenderTree);
-
-function attachComponentToElement(browserRendererId: number, elementSelector: System_String, componentId: number) {
+export function attachComponentToElement(browserRendererId: number, elementSelector: System_String, componentId: number) {
   const elementSelectorJs = platform.toJavaScriptString(elementSelector);
   const element = document.querySelector(elementSelectorJs);
   if (!element) {
@@ -28,7 +24,7 @@ function attachComponentToElement(browserRendererId: number, elementSelector: Sy
   browserRenderers[browserRendererId][componentId] = element;
 }
 
-function renderRenderTree(renderComponentArgs: Pointer) {
+export function renderRenderTree(renderComponentArgs: Pointer) {
   const browserRendererId = platform.readHeapInt32(renderComponentArgs, 0);
   const browserRenderer = browserRenderers[browserRendererId];
   if (!browserRenderer) {
diff --git a/src/Microsoft.Blazor.Browser/Interop/RegisteredFunction.cs b/src/Microsoft.Blazor.Browser/Interop/RegisteredFunction.cs
index 7d4ac60b23..07f188d8f2 100644
--- a/src/Microsoft.Blazor.Browser/Interop/RegisteredFunction.cs
+++ b/src/Microsoft.Blazor.Browser/Interop/RegisteredFunction.cs
@@ -24,7 +24,7 @@ namespace Microsoft.Blazor.Browser.Interop
             // This is a low-perf convenience method that bypasses the need to deal with
             // .NET memory and data structures on the JS side
             var argsJson = args.Select(Json.Serialize);
-            var resultJson = InvokeUnmarshalled<string>("__blazor_InvokeJson",
+            var resultJson = InvokeUnmarshalled<string>("invokeWithJsonMarshalling",
                 argsJson.Prepend(identifier).ToArray());
             return Json.Deserialize<TRes>(resultJson);
         }
diff --git a/src/Microsoft.Blazor.Browser/Rendering/BrowserRenderer.cs b/src/Microsoft.Blazor.Browser/Rendering/BrowserRenderer.cs
index 0d4667e177..a0b04e96a5 100644
--- a/src/Microsoft.Blazor.Browser/Rendering/BrowserRenderer.cs
+++ b/src/Microsoft.Blazor.Browser/Rendering/BrowserRenderer.cs
@@ -48,7 +48,7 @@ namespace Microsoft.Blazor.Browser.Rendering
         {
             var componentId = AssignComponentId(component);
             RegisteredFunction.InvokeUnmarshalled<int, string, int, object>(
-                "_blazorAttachComponentToElement",
+                "attachComponentToElement",
                 _browserRendererId,
                 domElementSelector,
                 componentId);
@@ -71,7 +71,7 @@ namespace Microsoft.Blazor.Browser.Rendering
             ArraySegment<RenderTreeNode> renderTree)
         {
             RegisteredFunction.InvokeUnmarshalled<RenderComponentArgs, object>(
-                "_blazorRender",
+                "renderRenderTree",
                 new RenderComponentArgs
                 {
                     BrowserRendererId = _browserRendererId,