diff --git a/src/d3d8/d3d8_d3d9_util.h b/src/d3d8/d3d8_d3d9_util.h
index ab0aa4d9b..d3ec7f7dd 100644
--- a/src/d3d8/d3d8_d3d9_util.h
+++ b/src/d3d8/d3d8_d3d9_util.h
@@ -78,33 +78,25 @@ namespace dxvk {
     // MultiSampleQuality is only used with D3DMULTISAMPLE_NONMASKABLE, which is not available in D3D8
     params.MultiSampleQuality = 0;
 
+    // If an application passes multiple D3DPRESENT_INTERVAL flags, this will be
+    // validated appropriately by D3D9. Simply copy the values here.
     UINT PresentationInterval = pParams->FullScreen_PresentationInterval;
 
     if (pParams->Windowed) {
-
-      if (unlikely(PresentationInterval != D3DPRESENT_INTERVAL_DEFAULT)) {
-        // TODO: what does dx8 do if windowed app sets FullScreen_PresentationInterval?
-        Logger::warn(str::format(
-          "D3D8: Application is windowed yet requested FullScreen_PresentationInterval ", PresentationInterval,
-          " (should be D3DPRESENT_INTERVAL_DEFAULT). This will be ignored."));
-      }
-
       // D3D8: For windowed swap chain, the back buffer is copied to the window immediately.
       PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;
     }
 
     D3DSWAPEFFECT SwapEffect = pParams->SwapEffect;
 
-    // D3DSWAPEFFECT_COPY_VSYNC has been removed
     if (SwapEffect == D3DSWAPEFFECT_COPY_VSYNC) {
-
+      // D3DSWAPEFFECT_COPY_VSYNC has been removed from D3D9, use D3DSWAPEFFECT_COPY
       SwapEffect = D3DSWAPEFFECT_COPY;
 
       // D3D8: In windowed mode, D3DSWAPEFFECT_COPY_VSYNC enables VSYNC.
       // In fullscreen, D3DPRESENT_INTERVAL_IMMEDIATE is meaningless.
-      if (pParams->Windowed || (PresentationInterval & D3DPRESENT_INTERVAL_IMMEDIATE) != 0) {
+      if (pParams->Windowed || PresentationInterval == D3DPRESENT_INTERVAL_IMMEDIATE) {
         PresentationInterval = D3DPRESENT_INTERVAL_ONE;
-        // TODO: what does dx8 do if multiple D3DPRESENT_INTERVAL flags are set?
       }
     }
 
diff --git a/src/d3d8/d3d8_device.cpp b/src/d3d8/d3d8_device.cpp
index 5298d96d0..d84c779b1 100644
--- a/src/d3d8/d3d8_device.cpp
+++ b/src/d3d8/d3d8_device.cpp
@@ -237,6 +237,12 @@ namespace dxvk {
               && pPresentationParameters->BackBufferCount > 1))
       return D3DERR_INVALIDCALL;
 
+    // In D3D8 nothing except D3DPRESENT_INTERVAL_DEFAULT can be used
+    // as a flag for windowed presentation.
+    if (unlikely(pPresentationParameters->Windowed
+              && pPresentationParameters->FullScreen_PresentationInterval != D3DPRESENT_INTERVAL_DEFAULT))
+      return D3DERR_INVALIDCALL;
+
     m_presentParams = *pPresentationParameters;
     ResetState();
 
diff --git a/src/d3d8/d3d8_interface.cpp b/src/d3d8/d3d8_interface.cpp
index 442bbe56f..502f3cfb8 100644
--- a/src/d3d8/d3d8_interface.cpp
+++ b/src/d3d8/d3d8_interface.cpp
@@ -129,6 +129,12 @@ namespace dxvk {
               && pPresentationParameters->BackBufferCount > 1))
       return D3DERR_INVALIDCALL;
 
+    // In D3D8 nothing except D3DPRESENT_INTERVAL_DEFAULT can be used
+    // as a flag for windowed presentation.
+    if (unlikely(pPresentationParameters->Windowed
+              && pPresentationParameters->FullScreen_PresentationInterval != D3DPRESENT_INTERVAL_DEFAULT))
+      return D3DERR_INVALIDCALL;
+
     Com<d3d9::IDirect3DDevice9> pDevice9 = nullptr;
     d3d9::D3DPRESENT_PARAMETERS params = ConvertPresentParameters9(pPresentationParameters);
     HRESULT res = m_d3d9->CreateDevice(
diff --git a/src/d3d9/d3d9_interface.cpp b/src/d3d9/d3d9_interface.cpp
index 46ec5d654..4ed2dfdf2 100644
--- a/src/d3d9/d3d9_interface.cpp
+++ b/src/d3d9/d3d9_interface.cpp
@@ -457,6 +457,13 @@ namespace dxvk {
               || pPresentationParameters->PresentationInterval == D3DPRESENT_INTERVAL_IMMEDIATE)))
       return D3DERR_INVALIDCALL;
 
+    // In windowed mode, only a subset of the presentation interval flags can be used.
+    if (unlikely(pPresentationParameters->Windowed
+            && !(pPresentationParameters->PresentationInterval == D3DPRESENT_INTERVAL_DEFAULT
+              || pPresentationParameters->PresentationInterval == D3DPRESENT_INTERVAL_ONE
+              || pPresentationParameters->PresentationInterval == D3DPRESENT_INTERVAL_IMMEDIATE)))
+      return D3DERR_INVALIDCALL;
+
     return D3D_OK;
   }