diff --git a/dom/canvas/WebGL2ContextBuffers.cpp b/dom/canvas/WebGL2ContextBuffers.cpp
index 7e77a40f59f8..c39b3419bae5 100644
--- a/dom/canvas/WebGL2ContextBuffers.cpp
+++ b/dom/canvas/WebGL2ContextBuffers.cpp
@@ -19,12 +19,17 @@ WebGL2Context::ValidateBufferTarget(GLenum target, const char* info)
     case LOCAL_GL_COPY_READ_BUFFER:
     case LOCAL_GL_COPY_WRITE_BUFFER:
     case LOCAL_GL_ELEMENT_ARRAY_BUFFER:
-    case LOCAL_GL_PIXEL_PACK_BUFFER:
-    case LOCAL_GL_PIXEL_UNPACK_BUFFER:
     case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER:
     case LOCAL_GL_UNIFORM_BUFFER:
         return true;
 
+    case LOCAL_GL_PIXEL_PACK_BUFFER:
+    case LOCAL_GL_PIXEL_UNPACK_BUFFER:
+        ErrorInvalidOperation("%s: PBOs are still under development, and are currently"
+                              " disabled.",
+                              info);
+        return false;
+
     default:
         ErrorInvalidEnumInfo(info, target);
         return false;
diff --git a/dom/canvas/WebGL2ContextRenderbuffers.cpp b/dom/canvas/WebGL2ContextRenderbuffers.cpp
index 7ad686414a3a..37141db32fb2 100644
--- a/dom/canvas/WebGL2ContextRenderbuffers.cpp
+++ b/dom/canvas/WebGL2ContextRenderbuffers.cpp
@@ -59,8 +59,14 @@ WebGL2Context::RenderbufferStorageMultisample(GLenum target, GLsizei samples,
                                               GLenum internalFormat,
                                               GLsizei width, GLsizei height)
 {
-  RenderbufferStorage_base("renderbufferStorageMultisample", target, samples,
-                           internalFormat, width, height);
+  const char funcName[] = "renderbufferStorageMultisample";
+  if (IsContextLost())
+    return;
+
+  //RenderbufferStorage_base(funcName, target, samples, internalFormat, width, height);
+
+  ErrorInvalidOperation("%s: Multisampling is still under development, and is currently"
+                        " disabled.", funcName);
 }
 
 } // namespace mozilla
diff --git a/dom/canvas/WebGL2ContextSamplers.cpp b/dom/canvas/WebGL2ContextSamplers.cpp
index e706d7ad8fe6..1dfa68e55e7b 100644
--- a/dom/canvas/WebGL2ContextSamplers.cpp
+++ b/dom/canvas/WebGL2ContextSamplers.cpp
@@ -12,15 +12,24 @@ namespace mozilla {
 already_AddRefed<WebGLSampler>
 WebGL2Context::CreateSampler()
 {
+    const char funcName[] = "createSampler";
+
     if (IsContextLost())
         return nullptr;
 
+    /*
     GLuint sampler;
     MakeContextCurrent();
     gl->fGenSamplers(1, &sampler);
 
     RefPtr<WebGLSampler> globj = new WebGLSampler(this, sampler);
     return globj.forget();
+    */
+
+    ErrorInvalidOperation("%s: Sampler objects are still under development, and are"
+                          " currently disabled.",
+                          funcName);
+    return nullptr;
 }
 
 void
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 80196fda6aba..c7803e140459 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -4204,11 +4204,16 @@ pref("webgl.max-warnings-per-context", 32);
 pref("webgl.enable-draft-extensions", false);
 pref("webgl.enable-privileged-extensions", false);
 pref("webgl.bypass-shader-validation", false);
-pref("webgl.enable-prototype-webgl2", false);
 pref("webgl.disable-fail-if-major-performance-caveat", false);
 pref("webgl.disable-DOM-blit-uploads", false);
 pref("webgl.webgl2-compat-mode", false);
 
+#ifdef NIGHTLY_BUILD
+pref("webgl.enable-prototype-webgl2", true);
+#else
+pref("webgl.enable-prototype-webgl2", false);
+#endif
+
 #ifdef RELEASE_BUILD
 // Keep this disabled on Release and Beta for now. (see bug 1171228)
 pref("webgl.enable-debug-renderer-info", false);