--- a/dom/canvas/WebGLContextDraw.cpp
+++ b/dom/canvas/WebGLContextDraw.cpp
@@ -507,16 +507,18 @@ WebGLContext::DrawArrays_check(const cha
 void
 WebGLContext::DrawArraysInstanced(GLenum mode, GLint first, GLsizei vertCount,
                                   GLsizei instanceCount, const char* const funcName)
 {
     AUTO_PROFILER_LABEL("WebGLContext::DrawArraysInstanced", GRAPHICS);
     if (IsContextLost())
         return;
 
+    const gl::GLContext::TlsScope inTls(gl);
+
     Maybe<uint32_t> lastVert;
     if (!DrawArrays_check(funcName, first, vertCount, instanceCount, &lastVert))
         return;
 
     bool error = false;
     const ScopedDrawHelper scopedHelper(this, funcName, mode, lastVert, instanceCount,
                                         &error);
     if (error)
@@ -663,16 +665,18 @@ void
 WebGLContext::DrawElementsInstanced(GLenum mode, GLsizei indexCount, GLenum type,
                                     WebGLintptr byteOffset, GLsizei instanceCount,
                                     const char* const funcName)
 {
     AUTO_PROFILER_LABEL("WebGLContext::DrawElementsInstanced", GRAPHICS);
     if (IsContextLost())
         return;
 
+    const gl::GLContext::TlsScope inTls(gl);
+
     Maybe<uint32_t> lastVert;
     if (!DrawElements_check(funcName, indexCount, type, byteOffset, instanceCount,
                             &lastVert))
     {
         return;
     }
 
     bool error = false;

--- a/gfx/gl/GLContext.cpp
+++ b/gfx/gl/GLContext.cpp
@@ -259,19 +259,19 @@ ChooseDebugFlags(CreateContextFlags crea
 #endif
 
     return debugFlags;
 }
 
 GLContext::GLContext(CreateContextFlags flags, const SurfaceCaps& caps,
                      GLContext* sharedContext, bool isOffscreen, bool useTLSIsCurrent)
   : mImplicitMakeCurrent(false),
+    mUseTLSIsCurrent(ShouldUseTLSIsCurrent(useTLSIsCurrent)),
     mIsOffscreen(isOffscreen),
     mContextLost(false),
-    mUseTLSIsCurrent(ShouldUseTLSIsCurrent(useTLSIsCurrent)),
     mVersion(0),
     mProfile(ContextProfile::Unknown),
     mShadingLanguageVersion(0),
     mVendor(GLVendor::Other),
     mRenderer(GLRenderer::Other),
     mTopError(LOCAL_GL_NO_ERROR),
     mDebugFlags(ChooseDebugFlags(flags)),
     mSharedContext(sharedContext),
@@ -3066,19 +3066,17 @@ GLContext::MakeCurrent(bool aForce) cons
             MOZ_ASSERT(IsCurrentImpl());
             return true;
         }
     }
 
     if (!MakeCurrentImpl())
         return false;
 
-    if (mUseTLSIsCurrent) {
-        sCurrentContext.set(reinterpret_cast<uintptr_t>(this));
-    }
+    sCurrentContext.set(reinterpret_cast<uintptr_t>(this));
     return true;
 }
 
 void
 GLContext::ResetSyncCallCount(const char* resetReason) const
 {
     if (ShouldSpew()) {
         printf_stderr("On %s, mSyncGLCallCount = %" PRIu64 "\n",

--- a/gfx/gl/GLContext.h
+++ b/gfx/gl/GLContext.h
@@ -194,16 +194,33 @@ class GLContext
     , public GenericAtomicRefCounted
     , public SupportsWeakPtr<GLContext>
 {
 public:
     MOZ_DECLARE_WEAKREFERENCE_TYPENAME(GLContext)
     static MOZ_THREAD_LOCAL(uintptr_t) sCurrentContext;
 
     bool mImplicitMakeCurrent;
+    bool mUseTLSIsCurrent;
+
+    class TlsScope final {
+        GLContext* const mGL;
+        const bool mWasTlsOk;
+    public:
+        explicit TlsScope(GLContext* const gl)
+            : mGL(gl)
+            , mWasTlsOk(gl->mUseTLSIsCurrent)
+        {
+            mGL->mUseTLSIsCurrent = true;
+        }
+
+        ~TlsScope() {
+            mGL->mUseTLSIsCurrent = mWasTlsOk;
+        }
+    };
 
 // -----------------------------------------------------------------------------
 // basic getters
 public:
 
     /**
      * Returns true if the context is using ANGLE. This should only be overridden
      * for an ANGLE implementation.
@@ -315,17 +332,16 @@ public:
      */
     virtual GLuint GetDefaultFramebuffer() {
         return 0;
     }
 
 protected:
     bool mIsOffscreen;
     mutable bool mContextLost;
-    const bool mUseTLSIsCurrent;
 
     /**
      * mVersion store the OpenGL's version, multiplied by 100. For example, if
      * the context is an OpenGL 2.1 context, mVersion value will be 210.
      */
     uint32_t mVersion;
     ContextProfile mProfile;