diff --git a/xpcom/build/IOInterposer.cpp b/xpcom/build/IOInterposer.cpp
index 34658958707..b8ae223f5af 100644
--- a/xpcom/build/IOInterposer.cpp
+++ b/xpcom/build/IOInterposer.cpp
@@ -157,9 +157,7 @@ IOInterposeObserver::Operation IOInterposer::sObservedOperations =
     sIsMainThread.set(isMainThread);
   }
   // Now we initialize the various interposers depending on platform
-#if defined(XP_WIN) || defined(XP_MACOSX)
   InitPoisonIOInterposer();
-#endif
   // We don't hook NSPR on Windows because PoisonIOInterposer captures a
   // superset of the former's events.
 #if !defined(XP_WIN)
diff --git a/xpcom/build/IOInterposer.h b/xpcom/build/IOInterposer.h
index 8ebd6a67e1d..e73ec1c0fd6 100644
--- a/xpcom/build/IOInterposer.h
+++ b/xpcom/build/IOInterposer.h
@@ -146,8 +146,6 @@ protected:
   static bool IsMainThread();
 };
 
-#ifdef MOZ_ENABLE_PROFILER_SPS
-
 /**
  * Class offering the public static IOInterposer API.
  *
@@ -260,34 +258,14 @@ public:
   RegisterCurrentThread(bool aIsMainThread = false);
 };
 
-#else /* MOZ_ENABLE_PROFILER_SPS */
-
-class IOInterposer MOZ_FINAL
-{
-  IOInterposer();
-public:
-  static inline void Init()                                               {}
-  static inline void Clear()                                              {}
-  static inline void Disable()                                            {}
-  static inline void Report(IOInterposeObserver::Observation& aOb)        {}
-  static inline void Register(IOInterposeObserver::Operation aOp,
-                              IOInterposeObserver* aObserver)             {}
-  static inline void Unregister(IOInterposeObserver::Operation aOp,
-                                IOInterposeObserver* aObserver)           {}
-  static inline bool IsObservedOperation(IOInterposeObserver::Operation aOp) {
-    return false;
-  }
-  static inline void RegisterCurrentThread(bool)                          {}
-};
-
-#endif /* MOZ_ENABLE_PROFILER_SPS */
-
 class IOInterposerInit
 {
 public:
   IOInterposerInit()
   {
+#if defined(MOZ_ENABLE_PROFILER_SPS)
     IOInterposer::Init();
+#endif
   }
 
   // No destructor needed at the moment -- this stuff stays active for the
diff --git a/xpcom/build/NSPRInterposer.h b/xpcom/build/NSPRInterposer.h
index f307146be34..342168663f6 100644
--- a/xpcom/build/NSPRInterposer.h
+++ b/xpcom/build/NSPRInterposer.h
@@ -5,8 +5,6 @@
 #ifndef NSPRINTERPOSER_H_
 #define NSPRINTERPOSER_H_
 
-#ifdef MOZ_ENABLE_PROFILER_SPS
-
 namespace mozilla {
 
 /**
@@ -25,6 +23,4 @@ void ClearNSPRIOInterposing();
 
 } // namespace mozilla
 
-#endif // MOZ_ENABLE_PROFILER_SPS
-
 #endif // NSPRINTERPOSER_H_
diff --git a/xpcom/build/PoisonIOInterposer.h b/xpcom/build/PoisonIOInterposer.h
index 87fb932fc3f..b3ef0d3b034 100644
--- a/xpcom/build/PoisonIOInterposer.h
+++ b/xpcom/build/PoisonIOInterposer.h
@@ -26,7 +26,7 @@ void MozillaUnRegisterDebugFILE(FILE *f);
 
 MOZ_END_EXTERN_C
 
-#if defined(MOZ_ENABLE_PROFILER_SPS) && (defined(XP_WIN) || defined(XP_MACOSX))
+#if defined(XP_WIN) || defined(XP_MACOSX)
 
 #ifdef __cplusplus
 namespace mozilla {
@@ -63,7 +63,7 @@ void ClearPoisonIOInterposer();
 } // namespace mozilla
 #endif /* __cplusplus */
 
-#else /* MOZ_ENABLE_PROFILER_SPS && (XP_WIN || XP_MACOSX) */
+#else /* XP_WIN || XP_MACOSX */
 
 #ifdef __cplusplus
 namespace mozilla {
@@ -76,6 +76,6 @@ inline void OnlyReportDirtyWrites(){}
 } // namespace mozilla
 #endif /* __cplusplus */
 
-#endif /* MOZ_ENABLE_PROFILER_SPS && (XP_WIN || XP_MACOSX) */
+#endif /* XP_WIN || XP_MACOSX */
 
 #endif // mozilla_PoisonIOInterposer_h
diff --git a/xpcom/build/PoisonIOInterposerStub.cpp b/xpcom/build/PoisonIOInterposerStub.cpp
index addca3b1d76..4929cc4b493 100644
--- a/xpcom/build/PoisonIOInterposerStub.cpp
+++ b/xpcom/build/PoisonIOInterposerStub.cpp
@@ -8,8 +8,6 @@
 
 extern "C" {
 
-  // Define empty implementations so we can compile when
-  // MOZ_ENABLE_PROFILER_SPS is undefined
   void MozillaRegisterDebugFD(int fd) {}
   void MozillaRegisterDebugFILE(FILE *f) {}
   void MozillaUnRegisterDebugFD(int fd) {}
diff --git a/xpcom/build/moz.build b/xpcom/build/moz.build
index d8738f79270..13f804661ba 100644
--- a/xpcom/build/moz.build
+++ b/xpcom/build/moz.build
@@ -27,15 +27,12 @@ EXPORTS.mozilla += [
 if CONFIG['OS_ARCH'] == 'WINNT':
     EXPORTS += ['nsWindowsDllInterceptor.h']
     EXPORTS.mozilla += ['perfprobe.h']
-    SOURCES += ['perfprobe.cpp']
-    if CONFIG['MOZ_ENABLE_PROFILER_SPS']:
-        SOURCES += [
-            'PoisonIOInterposerBase.cpp',
-            'PoisonIOInterposerWin.cpp',
-        ]
-    else:
-        SOURCES += ['PoisonIOInterposerStub.cpp']
-elif CONFIG['OS_ARCH'] == 'Darwin' and CONFIG['MOZ_ENABLE_PROFILER_SPS']:
+    SOURCES += [
+        'perfprobe.cpp',
+        'PoisonIOInterposerBase.cpp',
+        'PoisonIOInterposerWin.cpp',
+    ]
+elif CONFIG['OS_ARCH'] == 'Darwin':
     SOURCES += [
         'mach_override.c',
         'PoisonIOInterposerBase.cpp',
@@ -51,20 +48,17 @@ UNIFIED_SOURCES += xpcom_glue_src_cppsrcs
 
 UNIFIED_SOURCES += [
     'FrozenFunctions.cpp',
+    'IOInterposer.cpp',
     'LateWriteChecks.cpp',
     'nsXPComInit.cpp',
     'nsXPCOMStrings.cpp',
     'Services.cpp',
 ]
 
-if CONFIG['MOZ_ENABLE_PROFILER_SPS']:
+if CONFIG['OS_ARCH'] != 'WINNT':
     SOURCES += [
-        'IOInterposer.cpp',
+        'NSPRInterposer.cpp',
     ]
-    if CONFIG['OS_ARCH'] != 'WINNT':
-      SOURCES += [
-          'NSPRInterposer.cpp',
-      ]
 
 # FileLocation.cpp and Omnijar.cpp cannot be built in unified mode because they
 # use plarena.h.