diff --git a/SoObjects/Mailer/GNUmakefile b/SoObjects/Mailer/GNUmakefile
index aca1f240b..39a11ee62 100644
--- a/SoObjects/Mailer/GNUmakefile
+++ b/SoObjects/Mailer/GNUmakefile
@@ -37,6 +37,7 @@ Mailer_OBJC_FILES += \
 	\
 	EOQualifier+MailDAV.m		\
 	NSData+Mail.m			\
+	NSData+SMIME.m			\
 	NSDictionary+Mail.m		\
 	NSString+Mail.m			\
 	SOGoUser+Mailer.m