diff --git a/cmake/core-files.cmake b/cmake/core-files.cmake
index f9081e69c..2fc17af76 100644
--- a/cmake/core-files.cmake
+++ b/cmake/core-files.cmake
@@ -81,6 +81,8 @@ set(MBGL_CORE_FILES
     src/mbgl/gl/context.hpp
     src/mbgl/gl/debugging.cpp
     src/mbgl/gl/debugging.hpp
+    src/mbgl/gl/extension.cpp
+    src/mbgl/gl/extension.hpp
     src/mbgl/gl/gl.cpp
     src/mbgl/gl/object.cpp
     src/mbgl/gl/object.hpp
@@ -88,6 +90,8 @@ set(MBGL_CORE_FILES
     src/mbgl/gl/types.hpp
     src/mbgl/gl/value.cpp
     src/mbgl/gl/value.hpp
+    src/mbgl/gl/vertex_array.cpp
+    src/mbgl/gl/vertex_array.hpp
 
     # layout
     src/mbgl/layout/clip_lines.cpp
diff --git a/include/mbgl/gl/gl.hpp b/include/mbgl/gl/gl.hpp
index c849a935c..a499d731d 100644
--- a/include/mbgl/gl/gl.hpp
+++ b/include/mbgl/gl/gl.hpp
@@ -1,8 +1,6 @@
 #pragma once
 
-#include <string>
 #include <stdexcept>
-#include <vector>
 
 #if __APPLE__
     #include "TargetConditionals.h"
@@ -38,51 +36,12 @@ struct Error : std::runtime_error {
 
 void checkError(const char *cmd, const char *file, int line);
 
+} // namespace gl
+} // namespace mbgl
+
 #ifndef NDEBUG
 #define MBGL_CHECK_ERROR(cmd) ([&]() { struct __MBGL_C_E { ~__MBGL_C_E() { ::mbgl::gl::checkError(#cmd, __FILE__, __LINE__); } } __MBGL_C_E; return cmd; }())
 #else
 #define MBGL_CHECK_ERROR(cmd) (cmd)
 #endif
 
-class ExtensionFunctionBase {
-public:
-    static std::vector<ExtensionFunctionBase*>& functions();
-    typedef std::pair<const char *, const char *> Probe;
-    std::vector<Probe> probes;
-    void (*ptr)();
-};
-
-template <class>
-class ExtensionFunction;
-
-template <class R, class... Args>
-class ExtensionFunction<R (Args...)> : protected ExtensionFunctionBase {
-public:
-    ExtensionFunction(std::initializer_list<Probe> probes_) {
-        probes = probes_;
-        ExtensionFunctionBase::functions().push_back(this);
-    }
-
-    explicit operator bool() const {
-        return ptr;
-    }
-
-    R operator()(Args... args) const {
-        return (*reinterpret_cast<R (*)(Args...)>(ptr))(std::forward<Args>(args)...);
-    }
-};
-
-using glProc = void (*)();
-void InitializeExtensions(glProc (*getProcAddress)(const char *));
-
-extern ExtensionFunction<void (GLuint array)>
-    BindVertexArray;
-
-extern ExtensionFunction<void (GLsizei n, const GLuint* arrays)>
-    DeleteVertexArrays;
-
-extern ExtensionFunction<void (GLsizei n, GLuint* arrays)>
-    GenVertexArrays;
-
-} // namespace gl
-} // namespace mbgl
diff --git a/include/mbgl/platform/default/headless_view.hpp b/include/mbgl/platform/default/headless_view.hpp
index baa6a0382..23f1e8251 100644
--- a/include/mbgl/platform/default/headless_view.hpp
+++ b/include/mbgl/platform/default/headless_view.hpp
@@ -23,6 +23,7 @@ typedef XID GLXPbuffer;
 #include <mbgl/mbgl.hpp>
 #include <mbgl/gl/gl.hpp>
 #include <mbgl/gl/types.hpp>
+#include <mbgl/gl/extension.hpp>
 
 #include <memory>
 #include <thread>
diff --git a/platform/android/src/native_map_view.cpp b/platform/android/src/native_map_view.cpp
index 33ba115b9..2714b832e 100755
--- a/platform/android/src/native_map_view.cpp
+++ b/platform/android/src/native_map_view.cpp
@@ -15,6 +15,7 @@
 #include <mbgl/platform/platform.hpp>
 #include <mbgl/platform/event.hpp>
 #include <mbgl/platform/log.hpp>
+#include <mbgl/gl/extension.hpp>
 #include <mbgl/gl/gl.hpp>
 #include <mbgl/util/constants.hpp>
 
diff --git a/platform/default/glfw_view.cpp b/platform/default/glfw_view.cpp
index 17b233a41..fa5190c80 100644
--- a/platform/default/glfw_view.cpp
+++ b/platform/default/glfw_view.cpp
@@ -3,6 +3,7 @@
 #include <mbgl/sprite/sprite_image.hpp>
 #include <mbgl/style/transition_options.hpp>
 #include <mbgl/gl/gl.hpp>
+#include <mbgl/gl/extension.hpp>
 #include <mbgl/platform/log.hpp>
 #include <mbgl/platform/platform.hpp>
 #include <mbgl/util/string.hpp>
diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index f2a365f45..4d660f8f3 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -1,7 +1,7 @@
 #import "MGLMapView_Private.h"
 
 #include <mbgl/platform/log.hpp>
-#include <mbgl/gl/gl.hpp>
+#include <mbgl/gl/extension.hpp>
 
 #import <GLKit/GLKit.h>
 #import <OpenGLES/EAGL.h>
diff --git a/platform/macos/src/MGLMapView.mm b/platform/macos/src/MGLMapView.mm
index 13ec4508d..b40f6ebc6 100644
--- a/platform/macos/src/MGLMapView.mm
+++ b/platform/macos/src/MGLMapView.mm
@@ -22,6 +22,7 @@
 #import <mbgl/annotation/annotation.hpp>
 #import <mbgl/map/camera.hpp>
 #import <mbgl/platform/darwin/reachability.h>
+#import <mbgl/gl/extension.hpp>
 #import <mbgl/gl/gl.hpp>
 #import <mbgl/sprite/sprite_image.hpp>
 #import <mbgl/storage/default_file_source.hpp>
diff --git a/platform/qt/src/qmapbox.cpp b/platform/qt/src/qmapbox.cpp
index 7e7a3c5f8..118b1355e 100644
--- a/platform/qt/src/qmapbox.cpp
+++ b/platform/qt/src/qmapbox.cpp
@@ -1,6 +1,6 @@
 #include "qmapbox.hpp"
 
-#include <mbgl/gl/gl.hpp>
+#include <mbgl/gl/extension.hpp>
 #include <mbgl/map/change.hpp>
 #include <mbgl/storage/network_status.hpp>
 #include <mbgl/util/default_styles.hpp>
diff --git a/src/mbgl/geometry/vao.cpp b/src/mbgl/geometry/vao.cpp
index 214ed7a88..2c5e1677f 100644
--- a/src/mbgl/geometry/vao.cpp
+++ b/src/mbgl/geometry/vao.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/geometry/vao.hpp>
+#include <mbgl/gl/vertex_array.hpp>
 #include <mbgl/platform/log.hpp>
 #include <mbgl/util/string.hpp>
 #include <mbgl/gl/gl.hpp>
diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 3c1b5e45a..ae50e64cb 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/gl/context.hpp>
 #include <mbgl/gl/gl.hpp>
+#include <mbgl/gl/vertex_array.hpp>
 #include <mbgl/util/traits.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/gl/debugging.cpp b/src/mbgl/gl/debugging.cpp
index e61de42bc..943710ab7 100644
--- a/src/mbgl/gl/debugging.cpp
+++ b/src/mbgl/gl/debugging.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/gl/debugging.hpp>
 #include <mbgl/gl/gl.hpp>
+#include <mbgl/gl/extension.hpp>
 #include <mbgl/platform/event.hpp>
 #include <mbgl/platform/log.hpp>
 
diff --git a/src/mbgl/gl/extension.cpp b/src/mbgl/gl/extension.cpp
new file mode 100644
index 000000000..ee94e8ecf
--- /dev/null
+++ b/src/mbgl/gl/extension.cpp
@@ -0,0 +1,48 @@
+#include <mbgl/gl/extension.hpp>
+#include <mbgl/gl/gl.hpp>
+
+#include <mutex>
+#include <string>
+#include <vector>
+
+namespace mbgl {
+namespace gl {
+namespace detail {
+
+using Probes = std::vector<ExtensionFunctionBase::Probe>;
+using ExtensionFunctions = std::vector<std::pair<glProc*, Probes>>;
+ExtensionFunctions& extensionFunctions() {
+    static ExtensionFunctions functions;
+    return functions;
+}
+
+ExtensionFunctionBase::ExtensionFunctionBase(std::initializer_list<Probe> probes) {
+    extensionFunctions().emplace_back(&ptr, probes);
+}
+
+} // namespace detail
+
+static std::once_flag initializeExtensionsOnce;
+
+void InitializeExtensions(glProc (*getProcAddress)(const char*)) {
+    std::call_once(initializeExtensionsOnce, [getProcAddress] {
+        const char* extensionsPtr =
+            reinterpret_cast<const char*>(MBGL_CHECK_ERROR(glGetString(GL_EXTENSIONS)));
+
+        if (!extensionsPtr)
+            return;
+
+        const std::string extensions = extensionsPtr;
+        for (auto fn : detail::extensionFunctions()) {
+            for (auto probe : fn.second) {
+                if (extensions.find(probe.first) != std::string::npos) {
+                    *fn.first = getProcAddress(probe.second);
+                    break;
+                }
+            }
+        }
+    });
+}
+
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/gl/extension.hpp b/src/mbgl/gl/extension.hpp
new file mode 100644
index 000000000..ea5a1ae5f
--- /dev/null
+++ b/src/mbgl/gl/extension.hpp
@@ -0,0 +1,41 @@
+#pragma once
+
+#include <initializer_list>
+#include <utility>
+
+namespace mbgl {
+namespace gl {
+
+using glProc = void (*)();
+void InitializeExtensions(glProc (*getProcAddress)(const char*));
+
+namespace detail {
+
+class ExtensionFunctionBase {
+public:
+    using Probe = std::pair<const char*, const char*>;
+    ExtensionFunctionBase(std::initializer_list<Probe>);
+    glProc ptr;
+};
+
+} // namespace detail
+
+template <class>
+class ExtensionFunction;
+
+template <class R, class... Args>
+class ExtensionFunction<R(Args...)> : protected detail::ExtensionFunctionBase {
+public:
+    using detail::ExtensionFunctionBase::ExtensionFunctionBase;
+
+    explicit operator bool() const {
+        return ptr;
+    }
+
+    R operator()(Args... args) const {
+        return (*reinterpret_cast<R (*)(Args...)>(ptr))(std::forward<Args>(args)...);
+    }
+};
+
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/gl/gl.cpp b/src/mbgl/gl/gl.cpp
index 2040ff057..5cef25416 100644
--- a/src/mbgl/gl/gl.cpp
+++ b/src/mbgl/gl/gl.cpp
@@ -1,63 +1,9 @@
 #include <mbgl/gl/gl.hpp>
 #include <mbgl/util/string.hpp>
-#include <mbgl/platform/log.hpp>
-
-#include <cassert>
-#include <iostream>
-#include <unordered_map>
-#include <mutex>
 
 namespace mbgl {
 namespace gl {
 
-ExtensionFunction<void (GLuint array)>
-    BindVertexArray({
-        {"GL_ARB_vertex_array_object", "glBindVertexArray"},
-        {"GL_OES_vertex_array_object", "glBindVertexArrayOES"},
-        {"GL_APPLE_vertex_array_object", "glBindVertexArrayAPPLE"}
-    });
-
-ExtensionFunction<void (GLsizei n, const GLuint* arrays)>
-    DeleteVertexArrays({
-        {"GL_ARB_vertex_array_object", "glDeleteVertexArrays"},
-        {"GL_OES_vertex_array_object", "glDeleteVertexArraysOES"},
-        {"GL_APPLE_vertex_array_object", "glDeleteVertexArraysAPPLE"}
-    });
-
-ExtensionFunction<void (GLsizei n, GLuint* arrays)>
-    GenVertexArrays({
-        {"GL_ARB_vertex_array_object", "glGenVertexArrays"},
-        {"GL_OES_vertex_array_object", "glGenVertexArraysOES"},
-        {"GL_APPLE_vertex_array_object", "glGenVertexArraysAPPLE"}
-    });
-
-std::vector<ExtensionFunctionBase*>& ExtensionFunctionBase::functions() {
-    static std::vector<ExtensionFunctionBase*> functions;
-    return functions;
-}
-
-static std::once_flag initializeExtensionsOnce;
-
-void InitializeExtensions(glProc (*getProcAddress)(const char *)) {
-    std::call_once(initializeExtensionsOnce, [getProcAddress] {
-        const char * extensionsPtr = reinterpret_cast<const char *>(
-            MBGL_CHECK_ERROR(glGetString(GL_EXTENSIONS)));
-
-        if (!extensionsPtr)
-            return;
-
-        const std::string extensions = extensionsPtr;
-        for (auto fn : ExtensionFunctionBase::functions()) {
-            for (auto probe : fn->probes) {
-                if (extensions.find(probe.first) != std::string::npos) {
-                    fn->ptr = getProcAddress(probe.second);
-                    break;
-                }
-            }
-        }
-    });
-}
-
 namespace {
 
 constexpr const char* stringFromError(GLenum err) {
diff --git a/src/mbgl/gl/value.cpp b/src/mbgl/gl/value.cpp
index ae7d648a4..e78b97ef2 100644
--- a/src/mbgl/gl/value.cpp
+++ b/src/mbgl/gl/value.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/gl/value.hpp>
 #include <mbgl/gl/gl.hpp>
+#include <mbgl/gl/vertex_array.hpp>
 
 namespace mbgl {
 namespace gl {
diff --git a/src/mbgl/gl/vertex_array.cpp b/src/mbgl/gl/vertex_array.cpp
new file mode 100644
index 000000000..df63bbc4b
--- /dev/null
+++ b/src/mbgl/gl/vertex_array.cpp
@@ -0,0 +1,22 @@
+#include <mbgl/gl/vertex_array.hpp>
+
+namespace mbgl {
+namespace gl {
+
+ExtensionFunction<void(GLuint array)>
+    BindVertexArray({ { "GL_ARB_vertex_array_object", "glBindVertexArray" },
+                      { "GL_OES_vertex_array_object", "glBindVertexArrayOES" },
+                      { "GL_APPLE_vertex_array_object", "glBindVertexArrayAPPLE" } });
+
+ExtensionFunction<void(GLsizei n, const GLuint* arrays)>
+    DeleteVertexArrays({ { "GL_ARB_vertex_array_object", "glDeleteVertexArrays" },
+                         { "GL_OES_vertex_array_object", "glDeleteVertexArraysOES" },
+                         { "GL_APPLE_vertex_array_object", "glDeleteVertexArraysAPPLE" } });
+
+ExtensionFunction<void(GLsizei n, GLuint* arrays)>
+    GenVertexArrays({ { "GL_ARB_vertex_array_object", "glGenVertexArrays" },
+                      { "GL_OES_vertex_array_object", "glGenVertexArraysOES" },
+                      { "GL_APPLE_vertex_array_object", "glGenVertexArraysAPPLE" } });
+
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/gl/vertex_array.hpp b/src/mbgl/gl/vertex_array.hpp
new file mode 100644
index 000000000..6215e56f2
--- /dev/null
+++ b/src/mbgl/gl/vertex_array.hpp
@@ -0,0 +1,14 @@
+#pragma once
+
+#include <mbgl/gl/extension.hpp>
+#include <mbgl/gl/gl.hpp>
+
+namespace mbgl {
+namespace gl {
+
+extern ExtensionFunction<void(GLuint array)> BindVertexArray;
+extern ExtensionFunction<void(GLsizei n, const GLuint* arrays)> DeleteVertexArrays;
+extern ExtensionFunction<void(GLsizei n, GLuint* arrays)> GenVertexArrays;
+
+} // namespace gl
+} // namespace mbgl
\ No newline at end of file