diff --git a/modules/libpref/public/Makefile.in b/modules/libpref/public/Makefile.in
index 78d87752719b..924a2afc237d 100644
--- a/modules/libpref/public/Makefile.in
+++ b/modules/libpref/public/Makefile.in
@@ -45,6 +45,8 @@ include $(DEPTH)/config/autoconf.mk
 MODULE		= pref
 GRE_MODULE	= 1
 
+EXPORTS_NAMESPACES = mozilla
+
 SDK_XPIDLSRCS   = \
               nsIPrefService.idl \
               nsIPrefBranch.idl \
@@ -59,7 +61,11 @@ XPIDLSRCS	= \
 
 EXPORTS     = \
               PPrefTuple.h \
-              PrefTuple.h
+              PrefTuple.h \
+              $(NULL)
+
+EXPORTS_mozilla = \
+              Preferences.h \
               $(NULL)
 
 include $(topsrcdir)/config/rules.mk
diff --git a/modules/libpref/src/nsPrefService.h b/modules/libpref/public/Preferences.h
similarity index 93%
rename from modules/libpref/src/nsPrefService.h
rename to modules/libpref/public/Preferences.h
index 9bffbddf8da9..288e077b3bd3 100644
--- a/modules/libpref/src/nsPrefService.h
+++ b/modules/libpref/public/Preferences.h
@@ -37,8 +37,12 @@
  *
  * ***** END LICENSE BLOCK ***** */
 
-#ifndef nsPrefService_h__
-#define nsPrefService_h__
+#ifndef mozilla_Preferences_h
+#define mozilla_Preferences_h
+
+#ifndef MOZILLA_INTERNAL_API
+#error "This header is only usable from within libxul (MOZILLA_INTERNAL_API)."
+#endif
 
 #include "nsIPrefService.h"
 #include "nsIPrefBranch.h"
@@ -87,4 +91,4 @@ private:
 
 } // namespace mozilla
 
-#endif // nsPrefService_h__
+#endif // mozilla_Preferences_h
diff --git a/modules/libpref/src/Makefile.in b/modules/libpref/src/Makefile.in
index 1e0419b71f3f..58726e5ab4a2 100644
--- a/modules/libpref/src/Makefile.in
+++ b/modules/libpref/src/Makefile.in
@@ -55,10 +55,10 @@ LIBXUL_LIBRARY = 1
 
 CPPSRCS		= \
 			  nsPrefBranch.cpp	\
-			  nsPrefService.cpp	\
 			  nsPrefsFactory.cpp	\
 			  prefapi.cpp \
 			  prefread.cpp \
+			  Preferences.cpp	\
 			 $(NULL)
 
 DEFINES += -DOS_ARCH=$(OS_ARCH) \
diff --git a/modules/libpref/src/nsPrefService.cpp b/modules/libpref/src/Preferences.cpp
similarity index 99%
rename from modules/libpref/src/nsPrefService.cpp
rename to modules/libpref/src/Preferences.cpp
index 0b0a94b72e8f..640e76bd831b 100644
--- a/modules/libpref/src/nsPrefService.cpp
+++ b/modules/libpref/src/Preferences.cpp
@@ -40,7 +40,7 @@
 #include "mozilla/dom/ContentChild.h"
 #include "nsXULAppAPI.h"
 
-#include "nsPrefService.h"
+#include "mozilla/Preferences.h"
 #include "nsAppDirectoryServiceDefs.h"
 #include "nsDirectoryServiceDefs.h"
 #include "nsICategoryManager.h"
diff --git a/modules/libpref/src/nsPrefsFactory.cpp b/modules/libpref/src/nsPrefsFactory.cpp
index c09a04adc3b7..d61e0cc80c17 100644
--- a/modules/libpref/src/nsPrefsFactory.cpp
+++ b/modules/libpref/src/nsPrefsFactory.cpp
@@ -37,7 +37,7 @@
  * ***** END LICENSE BLOCK ***** */
 
 #include "mozilla/ModuleUtils.h"
-#include "nsPrefService.h"
+#include "mozilla/Preferences.h"
 #include "nsPrefBranch.h"
 #include "prefapi.h"