diff --git a/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp b/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
index 920d2c72d4fa..d212c686d9e7 100644
--- a/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
+++ b/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
@@ -299,6 +299,19 @@ Result<Ok, mozilla::ipc::LaunchError> SandboxBroker::LaunchApp(
         "Setting the reduced set of flags should always succeed");
   }
 
+  // Bug 1936749: MpDetours.dll injection is incompatible with ACG.
+  constexpr sandbox::MitigationFlags kDynamicCodeFlags =
+      sandbox::MITIGATION_DYNAMIC_CODE_DISABLE |
+      sandbox::MITIGATION_DYNAMIC_CODE_DISABLE_WITH_OPT_OUT;
+  sandbox::MitigationFlags delayedMitigations =
+      mPolicy->GetDelayedProcessMitigations();
+  if ((delayedMitigations & kDynamicCodeFlags) &&
+      ::GetModuleHandleW(L"MpDetours.dll")) {
+    delayedMitigations &= ~kDynamicCodeFlags;
+    SANDBOX_SUCCEED_OR_CRASH(
+        mPolicy->SetDelayedProcessMitigations(delayedMitigations));
+  }
+
   // If logging enabled, set up the policy.
   if (aEnableLogging) {
     ApplyLoggingPolicy();