diff --git a/src/main/java/com/replaymod/render/hooks/EntityRendererHandler.java b/src/main/java/com/replaymod/render/hooks/EntityRendererHandler.java
index e05d21ca..7695388b 100644
--- a/src/main/java/com/replaymod/render/hooks/EntityRendererHandler.java
+++ b/src/main/java/com/replaymod/render/hooks/EntityRendererHandler.java
@@ -41,6 +41,8 @@ public class EntityRendererHandler extends EventRegistrations implements WorldRe
 
     private final long startTime;
 
+    private long fakeFinishTimeNano;
+
     public EntityRendererHandler(RenderSettings settings, RenderInfo renderInfo) {
         this.settings = settings;
         this.renderInfo = renderInfo;
@@ -71,6 +73,7 @@ public class EntityRendererHandler extends EventRegistrations implements WorldRe
     }
 
     public void renderWorld(float partialTicks, long finishTimeNano) {
+        fakeFinishTimeNano = finishTimeNano;
         //#if MC>=11400
         PreRenderCallback.EVENT.invoker().preRender();
         //#else
@@ -142,6 +145,10 @@ public class EntityRendererHandler extends EventRegistrations implements WorldRe
         return this.renderInfo;
     }
 
+    public long getFakeFinishTimeNano() {
+        return fakeFinishTimeNano;
+    }
+
     public interface IEntityRenderer {
         void replayModRender_setHandler(EntityRendererHandler handler);
         EntityRendererHandler replayModRender_getHandler();
diff --git a/src/main/java/com/replaymod/render/mixin/Mixin_FakeSystemTimeUniforms_Iris.java b/src/main/java/com/replaymod/render/mixin/Mixin_FakeSystemTimeUniforms_Iris.java
new file mode 100644
index 00000000..21fcd479
--- /dev/null
+++ b/src/main/java/com/replaymod/render/mixin/Mixin_FakeSystemTimeUniforms_Iris.java
@@ -0,0 +1 @@
+// 1.21+
diff --git a/src/main/resources/mixins.render.replaymod.json b/src/main/resources/mixins.render.replaymod.json
index bd3761e4..28795704 100644
--- a/src/main/resources/mixins.render.replaymod.json
+++ b/src/main/resources/mixins.render.replaymod.json
@@ -14,6 +14,9 @@
     "Mixin_ChromaKeyColorSky",
     "Mixin_ChromaKeyDisableFog",
     "Mixin_ChromaKeyForceSky",
+    //#if MC>=12100
+    //$$ "Mixin_FakeSystemTimeUniforms_Iris",
+    //#endif
     "Mixin_ForceChunkLoading",
     "Mixin_HideNameTags",
     "Mixin_HideNameTags_LivingEntity",
diff --git a/versions/1.21/src/main/java/com/replaymod/render/mixin/Mixin_FakeSystemTimeUniforms_Iris.java b/versions/1.21/src/main/java/com/replaymod/render/mixin/Mixin_FakeSystemTimeUniforms_Iris.java
new file mode 100644
index 00000000..042d8008
--- /dev/null
+++ b/versions/1.21/src/main/java/com/replaymod/render/mixin/Mixin_FakeSystemTimeUniforms_Iris.java
@@ -0,0 +1,25 @@
+package com.replaymod.render.mixin;
+
+import com.replaymod.render.hooks.EntityRendererHandler;
+import net.irisshaders.iris.uniforms.SystemTimeUniforms;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.render.GameRenderer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Pseudo;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+
+@Pseudo
+@Mixin(value = SystemTimeUniforms.Timer.class, remap = false)
+public class Mixin_FakeSystemTimeUniforms_Iris {
+    @ModifyVariable(method = "beginFrame", at = @At("HEAD"), argsOnly = true)
+    private long useReplayTimeDuringRender(long frameStartTimeNs) {
+        GameRenderer gameRenderer = MinecraftClient.getInstance().gameRenderer;
+        EntityRendererHandler entityRendererHandler =
+            ((EntityRendererHandler.IEntityRenderer) gameRenderer).replayModRender_getHandler();
+        if (entityRendererHandler != null) {
+            frameStartTimeNs = entityRendererHandler.getFakeFinishTimeNano();
+        }
+        return frameStartTimeNs;
+    }
+}