diff --git a/src/rendervulkan.cpp b/src/rendervulkan.cpp
index 48bd78d..825545f 100644
--- a/src/rendervulkan.cpp
+++ b/src/rendervulkan.cpp
@@ -1279,8 +1279,6 @@ retry:
 	vecEnabledDeviceExtensions.push_back( VK_KHR_EXTERNAL_MEMORY_FD_EXTENSION_NAME );
 	vecEnabledDeviceExtensions.push_back( VK_EXT_EXTERNAL_MEMORY_DMA_BUF_EXTENSION_NAME );
 
-	vecEnabledDeviceExtensions.push_back( VK_KHR_SHADER_CLOCK_EXTENSION_NAME );
-
 	vecEnabledDeviceExtensions.push_back( VK_EXT_ROBUSTNESS_2_EXTENSION_NAME );
 
 	if ( supportsFp16 )
@@ -1302,11 +1300,6 @@ retry:
 		.pEnabledFeatures = 0,
 	};
 
-	VkPhysicalDeviceShaderClockFeaturesKHR clockFeatures = {};
-	clockFeatures.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SHADER_CLOCK_FEATURES_KHR;
-	clockFeatures.pNext = std::exchange(features2.pNext, &clockFeatures);
-	clockFeatures.shaderSubgroupClock = VK_TRUE;
-
 	VkPhysicalDeviceSamplerYcbcrConversionFeatures ycbcrFeatures = {};
 	ycbcrFeatures.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SAMPLER_YCBCR_CONVERSION_FEATURES;
 	ycbcrFeatures.pNext = std::exchange(features2.pNext, &ycbcrFeatures);
diff --git a/src/shaders/composite.h b/src/shaders/composite.h
index c0c902b..e243ef6 100644
--- a/src/shaders/composite.h
+++ b/src/shaders/composite.h
@@ -22,15 +22,23 @@ vec4 linearToSrgb(vec4 color) {
   return vec4(linearToSrgb(color.rgb), color.a);
 }
 
-void compositing_debug(uvec2 size, uvec2 coord) {
+uint pseudo_random(uint seed) {
+    seed ^= (seed << 13);
+    seed ^= (seed >> 17);
+    seed ^= (seed << 5);
+    return seed * 1664525u + 1013904223u;
+}
+
+void compositing_debug(uvec2 coord) {
     uvec2 pos = coord;
-    pos.x -= (u_frameId & 2) != 0 ? /* size.x - 160 */ 128 : 0;
-    pos.y -= (u_frameId & 1) != 0 ? /* size.y - 160 */ 128 : 0;
+    pos.x -= (u_frameId & 2) != 0 ?  128 : 0;
+    pos.y -= (u_frameId & 1) != 0 ?  128 : 0;
 
     if (pos.x >= 40 && pos.x < 120 && pos.y >= 40 && pos.y < 120) {
         vec4 value = vec4(1.0f, 1.0f, 1.0f, 1.0f);
         if (pos.x >= 48 && pos.x < 112 && pos.y >= 48 && pos.y < 112) {
-            vec4 time = round(unpackUnorm4x8(clock2x32ARB().x * 1664525u + 1013904223u)).xyzw;
+            uint random = pseudo_random(u_frameId.x + (pos.x & ~0x7) + (pos.y & ~0x7) * 50);
+            vec4 time = round(unpackUnorm4x8(random)).xyzw;
             if (time.x + time.y + time.z + time.w < 2.0f)
                 value = vec4(0.0f, 0.0f, 0.0f, 1.0f);
         }
diff --git a/src/shaders/cs_composite_blit.comp b/src/shaders/cs_composite_blit.comp
index 50e2f52..f07fc01 100644
--- a/src/shaders/cs_composite_blit.comp
+++ b/src/shaders/cs_composite_blit.comp
@@ -1,8 +1,7 @@
 #version 450
 
-#extension GL_GOOGLE_include_directive : require
 #extension GL_EXT_scalar_block_layout : require
-#extension GL_ARB_shader_clock : require
+#extension GL_GOOGLE_include_directive : require
 
 #include "descriptor_set.h"
 
@@ -57,5 +56,5 @@ void main() {
 
     // Indicator to quickly tell if we're in the compositing path or not.
     if (c_compositing_debug)
-        compositing_debug(outSize, coord);
+        compositing_debug(coord);
 }
diff --git a/src/shaders/cs_composite_rcas.comp b/src/shaders/cs_composite_rcas.comp
index e9b5b9a..b2db6b6 100644
--- a/src/shaders/cs_composite_rcas.comp
+++ b/src/shaders/cs_composite_rcas.comp
@@ -1,6 +1,5 @@
 #version 460
 
-#extension GL_ARB_shader_clock : require
 #extension GL_EXT_scalar_block_layout : require
 #extension GL_GOOGLE_include_directive : require
 
@@ -77,7 +76,7 @@ void rcasComposite(uvec2 pos)
     imageStore(dst, ivec2(pos), vec4(outputValue, undef));
 
     if (c_compositing_debug)
-        compositing_debug(uvec2(0), ivec2(pos));
+        compositing_debug(pos);
 }
 
 void main()