diff --git a/UI/MailPartViewers/GNUmakefile.preamble b/UI/MailPartViewers/GNUmakefile.preamble
index 15440fbddc..ea7a2d4650 100644
--- a/UI/MailPartViewers/GNUmakefile.preamble
+++ b/UI/MailPartViewers/GNUmakefile.preamble
@@ -1,3 +1,13 @@
+ifeq ($(HAS_LIBRARY_gnutls),yes)
+ADDITIONAL_CPPFLAGS += -DHAVE_GNUTLS=1
+SOGo_LIBRARIES_DEPEND_UPON += -lgnutls
+else
+ifeq ($(HAS_LIBRARY_ssl),yes)
+ADDITIONAL_CPPFLAGS += -DHAVE_OPENSSL=1
+SOGo_LIBRARIES_DEPEND_UPON += -lcrypto
+endif
+endif
+
 ifeq ($(HAS_LIBRARY_ssl),yes)
 ADDITIONAL_CPPFLAGS += -DHAVE_OPENSSL=1
 BUNDLE_LIBS += -lcrypto
diff --git a/UI/MailPartViewers/UIxMailPartSignedViewer.m b/UI/MailPartViewers/UIxMailPartSignedViewer.m
index 091777b906..e3c168f02f 100644
--- a/UI/MailPartViewers/UIxMailPartSignedViewer.m
+++ b/UI/MailPartViewers/UIxMailPartSignedViewer.m
@@ -18,7 +18,8 @@
  * Boston, MA 02111-1307, USA.
  */
 
-#ifdef HAVE_OPENSSL
+#if defined(HAVE_OPENSSL) || defined(HAVE_GNUTLS)
+
 #include <openssl/bio.h>
 #include <openssl/err.h>
 #include <openssl/pkcs7.h>
@@ -35,7 +36,8 @@
 
 @implementation UIxMailPartSignedViewer : UIxMailPartMixedViewer
 
-#ifdef HAVE_OPENSSL
+
+#if defined(HAVE_OPENSSL) || defined(HAVE_GNUTLS)
 - (BOOL) supportsSMIME
 {
   return YES;