--- a/mail/app/Makefile.in
+++ b/mail/app/Makefile.in
@@ -215,16 +215,17 @@ ifeq ($(OS_ARCH),OS2)
 RESFILE=splashos2.res
 RCFLAGS += -DMOZ_THUNDERBIRD
 ifdef BUILD_STATIC_LIBS
 RCFLAGS += -DMOZ_STATIC_BUILD -i $(DIST)/include/widget
 endif
 ifdef DEBUG
 RCFLAGS += -DDEBUG
 endif
+RCFLAGS += -DTHUNDERBIRD_ICO=\"$(DIST)/branding/thunderbird.ico\"
 endif
 
 LIBS += $(JEMALLOC_LIBS)
 
 include $(topsrcdir)/config/rules.mk
 
 ifdef MOZILLA_OFFICIAL
 DEFINES += -DMOZILLA_OFFICIAL

--- a/mail/app/splashos2.rc
+++ b/mail/app/splashos2.rc
@@ -40,17 +40,17 @@
 #include <os2.h>
 
 // Splash screen dialog ID.
 #define IDD_SPLASH  100
 
 // Splash screen bitmap ID.
 #define IDB_SPLASH  101
 
-ICON 1 "mozos2.ico"
+ICON 1 THUNDERBIRD_ICO
 
 DLGTEMPLATE IDD_SPLASH DISCARDABLE 
 BEGIN
     DIALOG "", IDD_SPLASH, 0, 0, 390, 261, , FCF_BORDER
     BEGIN
     END
 END
 

--- a/mail/branding/nightly/Makefile.in
+++ b/mail/branding/nightly/Makefile.in
@@ -71,15 +71,19 @@ endif
 ifeq ($(MOZ_WIDGET_TOOLKIT),gtk2)
 	cp $(srcdir)/mailicon16.png  $(DIST)/branding/default16.png
 	cp $(srcdir)/mailicon22.png  $(DIST)/branding/default22.png
 	cp $(srcdir)/mailicon24.png  $(DIST)/branding/default24.png
 	cp $(srcdir)/mailicon32.png  $(DIST)/branding/default32.png
 	cp $(srcdir)/mailicon48.png  $(DIST)/branding/default48.png
 	cp $(srcdir)/mailicon256.png $(DIST)/branding/default256.png
 endif
+ifeq ($(OS_ARCH),OS2)
+	cp $(srcdir)/thunderbird-os2.ico   $(DIST)/branding/thunderbird.ico
+endif
+
 # Now sort out the branding specific icons
 ifeq ($(OS_ARCH),WINNT)
 	cp $(srcdir)/windows/messengerWindow.ico  $(DIST)/branding/messengerWindow.ico
 endif
 ifeq ($(OS_ARCH),OS2)
 	cp $(srcdir)/os2/messengerWindow.ico  $(DIST)/branding/messengerWindow.ico
 endif

rename from mail/app/mozos2.ico
rename to mail/branding/nightly/thunderbird-os2.ico

--- a/other-licenses/branding/thunderbird/Makefile.in
+++ b/other-licenses/branding/thunderbird/Makefile.in
@@ -40,17 +40,16 @@ ifeq ($(MOZ_WIDGET_TOOLKIT),gtk2)
 	cp $(srcdir)/mailicon22.png  $(DIST)/branding/default22.png
 	cp $(srcdir)/mailicon24.png  $(DIST)/branding/default24.png
 	cp $(srcdir)/mailicon32.png  $(DIST)/branding/default32.png
 	cp $(srcdir)/mailicon48.png  $(DIST)/branding/default48.png
 	cp $(srcdir)/mailicon256.png $(DIST)/branding/default256.png
 endif
 ifeq ($(OS_ARCH),OS2)
 	cp $(srcdir)/thunderbird-os2.ico  $(DIST)/branding/thunderbird.ico
-	cp $(srcdir)/thunderbird-os2.ico  $(DIST)/branding/app.ico
 endif
 # Now sort out the branding specific icons
 ifeq ($(OS_ARCH),WINNT)
 	cp $(srcdir)/thunderbird.ico  $(DIST)/branding/messengerWindow.ico
 endif
 ifeq ($(OS_ARCH),OS2)
 	cp $(srcdir)/thunderbird-os2.ico  $(DIST)/branding/messengerWindow.ico
 endif