diff --git a/client/renderers/EGL/desktop.c b/client/renderers/EGL/desktop.c
index 2a9baa7d..f8f70597 100644
--- a/client/renderers/EGL/desktop.c
+++ b/client/renderers/EGL/desktop.c
@@ -42,6 +42,13 @@
 #include "postprocess.h"
 #include "filters.h"
 
+enum
+{
+  HDR_PEAK_LUMINANCE_MIN     = 80,
+  HDR_PEAK_LUMINANCE_DEFAULT = 10000,
+  HDR_PEAK_LUMINANCE_MAX     = 10000
+};
+
 struct DesktopShader
 {
   EGL_Shader * shader;
@@ -482,12 +489,24 @@ bool egl_desktopRender(EGL_Desktop * desktop, unsigned int outputWidth,
 
   *fullFrame = false;
   const bool hdr = desktop->hdr && !desktop->useSpice;
+  uint32_t hdrPeak = 0;
+  if (hdr)
+  {
+    hdrPeak = max(desktop->format.hdrMaxDisplayLuminance,
+        desktop->format.hdrMaxContentLightLevel);
+    if (!hdrPeak)
+      hdrPeak = HDR_PEAK_LUMINANCE_DEFAULT;
+    else
+      hdrPeak = clamp(hdrPeak,
+          HDR_PEAK_LUMINANCE_MIN, HDR_PEAK_LUMINANCE_MAX);
+  }
+
   const bool processFrame = atomic_exchange(&desktop->processFrame, false) ||
     egl_postProcessConfigModified(desktop->pp);
   if (processFrame &&
       egl_postProcessRun(desktop->pp, tex, desktop->mesh,
         width, height, outputWidth, outputHeight, dma,
-        hdr && desktop->hdrPQ) &&
+        hdr && desktop->hdrPQ, (float)hdrPeak) &&
       egl_postProcessNeedsFullFrame(desktop->pp))
   {
     /* The filter output may have changed everywhere, but this only applies to
diff --git a/client/renderers/EGL/filter.h b/client/renderers/EGL/filter.h
index acb43d7a..09498d42 100644
--- a/client/renderers/EGL/filter.h
+++ b/client/renderers/EGL/filter.h
@@ -33,6 +33,8 @@ typedef struct EGL_FilterRects
   EGL_DesktopRects * rects;
   GLfloat * matrix;
   int width, height;
+  /* zero for SDR, otherwise the HDR signal peak in cd/m² */
+  float hdrPeak;
 }
 EGL_FilterRects;
 
diff --git a/client/renderers/EGL/filter_ffx_cas.c b/client/renderers/EGL/filter_ffx_cas.c
index 0af01e74..2feb04c0 100644
--- a/client/renderers/EGL/filter_ffx_cas.c
+++ b/client/renderers/EGL/filter_ffx_cas.c
@@ -29,12 +29,15 @@
 #include "basic.vert.h"
 #include "ffx_cas.frag.h"
 
+#define CAS_SCRGB_REFERENCE_WHITE 80.0f
+
 typedef struct EGL_FilterFFXCAS
 {
   EGL_Filter base;
 
   EGL_Shader     * shader;
   EGL_Uniform    * uConsts;
+  EGL_Uniform    * uHDRScale;
   EGL_Effect     * effect;
   EGL_EffectPass * pass;
   bool             enable;
@@ -132,7 +135,8 @@ static bool egl_filterFFXCASInit(EGL_Filter ** filter)
     goto error_effect;
   }
 
-  this->uConsts = egl_shaderGetUniform(this->shader, "uConsts");
+  this->uConsts   = egl_shaderGetUniform(this->shader, "uConsts"  );
+  this->uHDRScale = egl_shaderGetUniform(this->shader, "uHDRScale");
   egl_filterFFXCASLoadState(&this->base);
 
   *filter = &this->base;
@@ -270,6 +274,10 @@ static EGL_Texture * egl_filterFFXCASRun(EGL_Filter * filter,
 {
   EGL_FilterFFXCAS * this = UPCAST(EGL_FilterFFXCAS, filter);
 
+  const float hdrScale = rects->hdrPeak > 0.0f ?
+    CAS_SCRGB_REFERENCE_WHITE / rects->hdrPeak : 0.0f;
+  egl_uniform1f(this->uHDRScale, hdrScale);
+
   return egl_effectRun(this->effect, rects, texture);
 }
 
diff --git a/client/renderers/EGL/postprocess.c b/client/renderers/EGL/postprocess.c
index 4052eb60..15119bfe 100644
--- a/client/renderers/EGL/postprocess.c
+++ b/client/renderers/EGL/postprocess.c
@@ -876,7 +876,8 @@ static bool configureChain(EGL_PostProcess * this, EGL_PixelFormat pixFmt,
 
 bool egl_postProcessRun(EGL_PostProcess * this, EGL_Texture * tex,
     EGL_DesktopRects * rects, int desktopWidth, int desktopHeight,
-    unsigned int targetX, unsigned int targetY, bool useDMA, bool hdrPQ)
+    unsigned int targetX, unsigned int targetY, bool useDMA, bool hdrPQ,
+    float hdrPeak)
 {
   if (targetX == 0 && targetY == 0)
     DEBUG_FATAL("targetX || targetY == 0");
@@ -918,10 +919,11 @@ bool egl_postProcessRun(EGL_PostProcess * this, EGL_Texture * tex,
   }
 
   EGL_FilterRects filterRects = {
-    .rects  = rects,
-    .matrix = this->matrix,
-    .width  = desktopWidth,
-    .height = desktopHeight,
+    .rects   = rects,
+    .matrix  = this->matrix,
+    .width   = desktopWidth,
+    .height  = desktopHeight,
+    .hdrPeak = hdrPeak,
   };
 
   EGL_Texture * texture = tex;
diff --git a/client/renderers/EGL/postprocess.h b/client/renderers/EGL/postprocess.h
index 063bc738..64029f95 100644
--- a/client/renderers/EGL/postprocess.h
+++ b/client/renderers/EGL/postprocess.h
@@ -47,7 +47,8 @@ bool egl_postProcessNeedsFullFrame(EGL_PostProcess * this);
  * targetX/Y is the final target output dimension hint if scalers are present */
 bool egl_postProcessRun(EGL_PostProcess * this, EGL_Texture * tex,
     EGL_DesktopRects * rects, int desktopWidth, int desktopHeight,
-    unsigned int targetX, unsigned int targetY, bool useDMA, bool hdrPQ);
+    unsigned int targetX, unsigned int targetY, bool useDMA, bool hdrPQ,
+    float hdrPeak);
 
 /* Return the current output texture and whether it remains PQ encoded. */
 EGL_Texture * egl_postProcessGetOutput(EGL_PostProcess * this,
diff --git a/client/renderers/EGL/shader/ffx_cas.frag b/client/renderers/EGL/shader/ffx_cas.frag
index b98150ad..273e888d 100644
--- a/client/renderers/EGL/shader/ffx_cas.frag
+++ b/client/renderers/EGL/shader/ffx_cas.frag
@@ -5,12 +5,14 @@ precision highp float;
 precision highp int;
 
 #include "compat.h"
+#include "hdr.h"
 
 in  vec2  fragCoord;
 out vec4  fragColor;
 
 uniform sampler2D sampler1;
 uniform uvec4     uConsts[2];
+uniform float     uHDRScale;
 
 #define A_GPU 1
 #define A_GLSL 1
@@ -19,7 +21,11 @@ uniform uvec4     uConsts[2];
 
 vec3 imageLoad(ivec2 point)
 {
-  return texelFetch(sampler1, point, 0).rgb;
+  vec3 color = texelFetch(sampler1, point, 0).rgb;
+  if (uHDRScale > 0.0)
+    color = max(bt709to2020(color * uHDRScale), vec3(0.0));
+
+  return color;
 }
 
 AF3 CasLoad(ASU2 p)
@@ -39,4 +45,9 @@ void main()
   CasFilter(
     fragColor.r, fragColor.g, fragColor.b,
     point, uConsts[0], uConsts[1], true);
+
+  if (uHDRScale > 0.0)
+    fragColor.rgb = bt2020to709(fragColor.rgb) / uHDRScale;
+
+  fragColor.a = 1.0;
 }