diff --git a/toolkit/xre/nsEmbedFunctions.cpp b/toolkit/xre/nsEmbedFunctions.cpp
index 357f6492f1f..912e0c99663 100644
--- a/toolkit/xre/nsEmbedFunctions.cpp
+++ b/toolkit/xre/nsEmbedFunctions.cpp
@@ -105,6 +105,8 @@
 #include "mozilla/ipc/TestShellParent.h"
 #include "mozilla/ipc/XPCShellEnvironment.h"
 
+#include "mozilla/Util.h" // for DebugOnly
+
 #ifdef MOZ_IPDL_TESTS
 #include "mozilla/_ipdltest/IPDLUnitTests.h"
 #include "mozilla/_ipdltest/IPDLUnitTestProcessChild.h"
@@ -417,7 +419,7 @@ XRE_InitChildProcess(int aArgc,
   NS_ABORT_IF_FALSE(!*end, "invalid parent PID");
 
   base::ProcessHandle parentHandle;
-  bool ok = base::OpenProcessHandle(parentPID, &parentHandle);
+  mozilla::DebugOnly<bool> ok = base::OpenProcessHandle(parentPID, &parentHandle);
   NS_ABORT_IF_FALSE(ok, "can't open handle to parent");
 
 #if defined(XP_WIN)
@@ -683,7 +685,7 @@ XRE_ShutdownChildProcess()
 {
   NS_ABORT_IF_FALSE(MessageLoopForUI::current(), "Wrong thread!");
 
-  MessageLoop* ioLoop = XRE_GetIOMessageLoop();
+  mozilla::DebugOnly<MessageLoop*> ioLoop = XRE_GetIOMessageLoop();
   NS_ABORT_IF_FALSE(!!ioLoop, "Bad shutdown order");
 
   // Quit() sets off the following chain of events