diff --git a/calendar/libical/src/libical/Makefile.in b/calendar/libical/src/libical/Makefile.in
index 5241638f53..bc1a04d7a1 100644
--- a/calendar/libical/src/libical/Makefile.in
+++ b/calendar/libical/src/libical/Makefile.in
@@ -42,18 +42,6 @@ ifneq (,$(filter BeOS Darwin OpenVMS NetBSD FreeBSD,$(OS_ARCH)))
 DEFINES	+= -D__USE_BSD=1
 endif
 
-INSTALL_TARGETS += ical
-ical_FILES := ical.h
-ical_DEST = $(DIST)/include
-ical_TARGET := export
-
-CSRCS += \
-	icalderivedparameter.c \
-	icalderivedproperty.c \
-	icalderivedvalue.c \
-	icalrestriction.c \
-	$(NULL)
-
 include $(moztopsrcdir)/config/rules.mk
 
 ######################################################################
diff --git a/calendar/libical/src/libical/moz.build b/calendar/libical/src/libical/moz.build
index 68b256a2db..6a15ccdc29 100644
--- a/calendar/libical/src/libical/moz.build
+++ b/calendar/libical/src/libical/moz.build
@@ -28,6 +28,28 @@ UNIFIED_SOURCES += [
     'vsnprintf.c',
 ]
 
+SOURCES += [
+    '!icalderivedparameter.c',
+    '!icalderivedproperty.c',
+    '!icalderivedvalue.c',
+    '!icalrestriction.c',
+]
+
+GENERATED_FILES += [
+    'ical.h',
+    'icalderivedparameter.c',
+    'icalderivedparameter.h',
+    'icalderivedproperty.c',
+    'icalderivedproperty.h',
+    'icalderivedvalue.c',
+    'icalderivedvalue.h',
+    'icalrestriction.c',
+]
+
+EXPORTS += [
+    '!ical.h'
+]
+
 # We allow warnings for third-party code that can be updated from upstream.
 AllowCompilerWarnings()