diff --git a/ext/native/thin3d/GLRenderManager.cpp b/ext/native/thin3d/GLRenderManager.cpp
index d66deb5d4f..57a80d79ec 100644
--- a/ext/native/thin3d/GLRenderManager.cpp
+++ b/ext/native/thin3d/GLRenderManager.cpp
@@ -633,9 +633,14 @@ size_t GLPushBuffer::GetTotalSize() const {
 
 void GLPushBuffer::MapDevice() {
 	for (auto &info : buffers_) {
+		if (!info.buffer->buffer) {
+			// Can't map - no device buffer associated yet.
+			continue;
+		}
+
 		assert(!info.deviceMemory);
 		// TODO: Can we use GL_WRITE_ONLY?
-		info.deviceMemory = (uint8_t *)info.buffer->Map(GL_READ_WRITE);
+		info.deviceMemory = (uint8_t *)info.buffer->Map(GL_READ_WRITE, GL_MAP_WRITE_BIT);
 
 		if (info.deviceMemory) {
 			delete[] info.localMemory;
@@ -664,3 +669,26 @@ void GLPushBuffer::UnmapDevice() {
 		}
 	}
 }
+
+void *GLRBuffer::Map(GLenum accessOld, GLbitfield accessNew) {
+	assert(buffer != 0);
+	glBindBuffer(target_, buffer);
+
+	void *p;
+	if (gl_extensions.VersionGEThan(3, 0, 0)) {
+		p = glMapBufferRange(target_, 0, size_, accessNew);
+	} else {
+#ifndef USING_GLES2
+	p = glMapBuffer(target_, accessOld);
+#endif
+	}
+
+	mapped_ = p != nullptr;
+	return p;
+}
+
+bool GLRBuffer::Unmap() {
+	glBindBuffer(target_, buffer);
+	mapped_ = false;
+	return glUnmapBuffer(target_) == GL_TRUE;
+}
diff --git a/ext/native/thin3d/GLRenderManager.h b/ext/native/thin3d/GLRenderManager.h
index bbf46c65f1..270dcb243b 100644
--- a/ext/native/thin3d/GLRenderManager.h
+++ b/ext/native/thin3d/GLRenderManager.h
@@ -139,18 +139,8 @@ public:
 		}
 	}
 
-	void *Map(GLenum access) {
-		glBindBuffer(target_, buffer);
-		void *p = glMapBuffer(target_, access);
-		mapped_ = p != nullptr;
-		return p;
-	}
-
-	bool Unmap() {
-		glBindBuffer(target_, buffer);
-		mapped_ = false;
-		return glUnmapBuffer(target_) == GL_TRUE;
-	}
+	void *Map(GLenum accessOld, GLbitfield accessNew);
+	bool Unmap();
 
 	bool Mapped() {
 		return mapped_;