diff --git a/mozglue/misc/MozProcessMitigationDynamicCodePolicy.h b/mozglue/misc/MozProcessMitigationDynamicCodePolicy.h
new file mode 100644
index 000000000000..c0fd11706737
--- /dev/null
+++ b/mozglue/misc/MozProcessMitigationDynamicCodePolicy.h
@@ -0,0 +1,38 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file is temporarily needed for bug 1766432. We plan to remove it
+// afterwards. Do not add new definitions here.
+
+#ifndef mozglue_misc_MozProcessMitigationDynamicCodePolicy_h__
+#define mozglue_misc_MozProcessMitigationDynamicCodePolicy_h__
+
+#include <winnt.h>
+
+// See bug 1766432 comment 4. We currently need to use our own definition
+// for PROCESS_MITIGATION_DYNAMIC_CODE_POLICY in MinGW builds.
+#if defined(__MINGW32__) || defined(__MINGW64__)
+
+typedef struct _MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY {
+  __C89_NAMELESS union {
+    DWORD Flags;
+    __C89_NAMELESS struct {
+      DWORD ProhibitDynamicCode : 1;
+      DWORD AllowThreadOptOut : 1;
+      DWORD AllowRemoteDowngrade : 1;
+      DWORD ReservedFlags : 29;
+    };
+  };
+} MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY;
+
+#else
+
+using MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY =
+    PROCESS_MITIGATION_DYNAMIC_CODE_POLICY;
+
+#endif  // defined(__MINGW32__) || defined(__MINGW64__)
+
+#endif  // mozglue_misc_MozProcessMitigationDynamicCodePolicy_h__
diff --git a/mozglue/misc/WindowsProcessMitigations.cpp b/mozglue/misc/WindowsProcessMitigations.cpp
index 79bc72ca8b85..bee281439bef 100644
--- a/mozglue/misc/WindowsProcessMitigations.cpp
+++ b/mozglue/misc/WindowsProcessMitigations.cpp
@@ -11,6 +11,11 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/DynamicallyLinkedFunctionPtr.h"
 
+// See bug 1766432 comment 4. In the future, we should keep this static assert
+// when we remove MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY.
+#include "mozilla/MozProcessMitigationDynamicCodePolicy.h"
+static_assert(sizeof(MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY) == 4);
+
 #if (_WIN32_WINNT < 0x0602)
 BOOL WINAPI GetProcessMitigationPolicy(
     HANDLE hProcess, PROCESS_MITIGATION_POLICY MitigationPolicy, PVOID lpBuffer,
@@ -60,7 +65,7 @@ MFBT_API bool IsDynamicCodeDisabled() {
     return false;
   }
 
-  PROCESS_MITIGATION_DYNAMIC_CODE_POLICY polInfo;
+  MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY polInfo;
   if (!pGetProcessMitigationPolicy(::GetCurrentProcess(),
                                    ProcessDynamicCodePolicy, &polInfo,
                                    sizeof(polInfo))) {
diff --git a/mozglue/misc/moz.build b/mozglue/misc/moz.build
index 6179461052c9..1b79cbaf6a01 100644
--- a/mozglue/misc/moz.build
+++ b/mozglue/misc/moz.build
@@ -75,6 +75,7 @@ if CONFIG["OS_ARCH"] == "WINNT":
     EXPORTS.mozilla += [
         "DynamicallyLinkedFunctionPtr.h",
         "ImportDir.h",
+        "MozProcessMitigationDynamicCodePolicy.h",
         "NativeNt.h",
         "WindowsDpiInitialization.h",
         "WindowsEnumProcessModules.h",
diff --git a/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp b/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp
index 0a569760274f..fff01e36ce06 100644
--- a/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp
+++ b/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp
@@ -21,6 +21,8 @@
 #include "nsWindowsDllInterceptor.h"
 #include "nsWindowsHelpers.h"
 
+#include "mozilla/MozProcessMitigationDynamicCodePolicy.h"
+
 NTSTATUS NTAPI NtFlushBuffersFile(HANDLE, PIO_STATUS_BLOCK);
 NTSTATUS NTAPI NtReadFile(HANDLE, HANDLE, PIO_APC_ROUTINE, PVOID,
                           PIO_STATUS_BLOCK, PVOID, ULONG, PLARGE_INTEGER,
@@ -850,7 +852,7 @@ bool TestDynamicCodePolicy() {
     return true;
   }
 
-  PROCESS_MITIGATION_DYNAMIC_CODE_POLICY policy = {};
+  MOZ_PROCESS_MITIGATION_DYNAMIC_CODE_POLICY policy = {};
   policy.ProhibitDynamicCode = true;
 
   mozilla::DynamicallyLinkedFunctionPtr<decltype(&SetProcessMitigationPolicy)>