diff --git a/browser/components/build/Makefile.in b/browser/components/build/Makefile.in
index a40b07015466..24832fd8b81b 100644
--- a/browser/components/build/Makefile.in
+++ b/browser/components/build/Makefile.in
@@ -37,7 +37,7 @@ CPPSRCS = nsModule.cpp \
           $(NULL)
 
 ifeq ($(OS_ARCH),WINNT)
-DEFINES += -DPSTOREC_DLL=\"$(WINDIR)\\system32\\pstorec.dll\"
+DEFINES += -DPSTOREC_DLL=\"$(subst \,\\,$(WINDIR))\\system32\\pstorec.dll\"
 
 OS_LIBS	+= $(call EXPAND_LIBNAME,ole32 shell32)
 endif
diff --git a/browser/components/migration/src/Makefile.in b/browser/components/migration/src/Makefile.in
index 2e8c5e97e364..9ee0d204415a 100644
--- a/browser/components/migration/src/Makefile.in
+++ b/browser/components/migration/src/Makefile.in
@@ -76,7 +76,7 @@ CPPSRCS  = nsProfileMigrator.cpp \
            $(NULL)
 
 ifeq ($(OS_ARCH),WINNT)
-DEFINES += -DPSTOREC_DLL=\"$(WINDIR)\\system32\\pstorec.dll\"
+DEFINES += -DPSTOREC_DLL=\"$(subst \,\\,$(WINDIR))\\system32\\pstorec.dll\"
 
 CPPSRCS += nsIEProfileMigrator.cpp \
            $(NULL)