diff --git a/renderdoc/driver/d3d11/d3d11_overlay.cpp b/renderdoc/driver/d3d11/d3d11_overlay.cpp
index 7ddd1e0f6..65a5c13b2 100644
--- a/renderdoc/driver/d3d11/d3d11_overlay.cpp
+++ b/renderdoc/driver/d3d11/d3d11_overlay.cpp
@@ -648,9 +648,6 @@ ResourceId D3D11Replay::RenderOverlay(ResourceId texid, CompType typeHint, Debug
 
     ID3D11Buffer *psbuf = GetDebugManager()->MakeCBuffer(&overdrawRamp[0].x, sizeof(overdrawRamp));
 
-    Vec4f viewport = Vec4f((float)details.texWidth, (float)details.texHeight);
-    ID3D11Buffer *gsbuf = GetDebugManager()->MakeCBuffer(&viewport.x, sizeof(viewport));
-
     float overlayConsts[] = {0.0f, 0.0f, 0.0f, 0.0f};
     m_pImmediateContext->ClearRenderTargetView(rtv, overlayConsts);
 
@@ -666,6 +663,11 @@ ResourceId D3D11Replay::RenderOverlay(ResourceId texid, CompType typeHint, Debug
 
     events.push_back(eventId);
 
+    D3D11_VIEWPORT view = m_pImmediateContext->GetCurrentPipelineState()->RS.Viewports[0];
+
+    Vec4f viewport = Vec4f(view.Width, view.Height);
+    ID3D11Buffer *gsbuf = GetDebugManager()->MakeCBuffer(&viewport.x, sizeof(viewport));
+
     for(size_t i = 0; i < events.size(); i++)
     {
       D3D11RenderState oldstate = *m_pImmediateContext->GetCurrentPipelineState();
diff --git a/renderdoc/driver/gl/gl_overlay.cpp b/renderdoc/driver/gl/gl_overlay.cpp
index 0818d3350..629fb854e 100644
--- a/renderdoc/driver/gl/gl_overlay.cpp
+++ b/renderdoc/driver/gl/gl_overlay.cpp
@@ -854,7 +854,7 @@ ResourceId GLReplay::RenderOverlay(ResourceId texid, CompType typeHint, DebugOve
     drv.glBindBuffer(eGL_COPY_WRITE_BUFFER, DebugData.UBOs[2]);
     v = (Vec4f *)drv.glMapBufferRange(eGL_COPY_WRITE_BUFFER, 0, sizeof(Vec4f),
                                       GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT);
-    *v = Vec4f((float)texDetails.width, (float)texDetails.height);
+    *v = Vec4f(rs.Viewports[0].width, rs.Viewports[0].height);
     drv.glUnmapBuffer(eGL_COPY_WRITE_BUFFER);
 
     vector<uint32_t> events = passEvents;