diff --git a/mozilla/calendar/lightning/Makefile.in b/mozilla/calendar/lightning/Makefile.in
index 322e5e34ec7..39eda5e1d4a 100644
--- a/mozilla/calendar/lightning/Makefile.in
+++ b/mozilla/calendar/lightning/Makefile.in
@@ -79,6 +79,7 @@ DEFINES += -DFIREFOX_VERSION=$(FIREFOX_VERSION)
 DEFINES += -DSEAMONKEY_VERSION=$(SEAMONKEY_VERSION)
 
 DEFINES += -DTARGET_PLATFORM=$(OS_TARGET)_$(TARGET_XPCOM_ABI)
+DEFINES += -DLIGHTNING_FIREFOX=$(LIGHTNING_FIREFOX)
 
 LIGHTNING_VERSION := $(shell cat $(srcdir)/../sunbird/config/version.txt)
 DEFINES += -DLIGHTNING_VERSION=$(LIGHTNING_VERSION)
diff --git a/mozilla/calendar/lightning/install.rdf b/mozilla/calendar/lightning/install.rdf
index e1f371ddf7a..d1246706b85 100644
--- a/mozilla/calendar/lightning/install.rdf
+++ b/mozilla/calendar/lightning/install.rdf
@@ -21,6 +21,7 @@
       </Description>
     </em:targetApplication>
 
+#if LIGHTNING_FIREFOX
     <!-- We only allow installation of Lightning into Firefox for ease of
        - development. You can edit the JS and then click reload in Firefox as
        - opposed to having to restart Thunderbird after each edit. -->
@@ -37,6 +38,7 @@
 #endif
       </Description>
     </em:targetApplication>
+#endif
 
 #ifndef MOZILLA_1_8_BRANCH
     <em:targetApplication>