diff --git a/src/rtt.cpp b/src/rtt.cpp
index 4c1d1ba..6aec616 100644
--- a/src/rtt.cpp
+++ b/src/rtt.cpp
@@ -508,7 +508,7 @@ glm::uint8_t* PBO::map() noexcept
 {
     App::I->render_task([this] {
         glBindBuffer(GL_PIXEL_PACK_BUFFER, buffer_id);
-        mapped_ptr = (GLubyte*)glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);
+        mapped_ptr = (GLubyte*)glMapBufferRange(GL_PIXEL_PACK_BUFFER, 0, width * height * 4, GL_MAP_READ_BIT);
         glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
     });
     return mapped_ptr;