diff --git a/include/air_modes_preamble.h b/include/air_modes_preamble.h
index 2158a5a..2b3aff3 100644
--- a/include/air_modes_preamble.h
+++ b/include/air_modes_preamble.h
@@ -24,17 +24,18 @@
 #define INCLUDED_AIR_MODES_PREAMBLE_H
 
 #include <gr_block.h>
+#include <air_modes_api.h>
 
 class air_modes_preamble;
 typedef boost::shared_ptr<air_modes_preamble> air_modes_preamble_sptr;
 
-air_modes_preamble_sptr air_make_modes_preamble(int channel_rate, float threshold_db);
+AIR_MODES_API air_modes_preamble_sptr air_make_modes_preamble(int channel_rate, float threshold_db);
 
 /*!
  * \brief mode select preamble detection
  * \ingroup block
  */
-class air_modes_preamble : public gr_block
+class AIR_MODES_API air_modes_preamble : public gr_block
 {
 private:
     friend air_modes_preamble_sptr air_make_modes_preamble(int channel_rate, float threshold_db);
diff --git a/include/air_modes_slicer.h b/include/air_modes_slicer.h
index 5fe1da3..eb9e6a6 100644
--- a/include/air_modes_slicer.h
+++ b/include/air_modes_slicer.h
@@ -25,17 +25,18 @@
 
 #include <gr_sync_block.h>
 #include <gr_msg_queue.h>
+#include <air_modes_api.h>
 
 class air_modes_slicer;
 typedef boost::shared_ptr<air_modes_slicer> air_modes_slicer_sptr;
 
-air_modes_slicer_sptr air_make_modes_slicer(int channel_rate, gr_msg_queue_sptr queue);
+AIR_MODES_API air_modes_slicer_sptr air_make_modes_slicer(int channel_rate, gr_msg_queue_sptr queue);
 
 /*!
  * \brief mode select slicer detection
  * \ingroup block
  */
-class air_modes_slicer : public gr_sync_block
+class AIR_MODES_API air_modes_slicer : public gr_sync_block
 {
 private:
     friend air_modes_slicer_sptr air_make_modes_slicer(int channel_rate, gr_msg_queue_sptr queue);
diff --git a/lib/air_modes_preamble.cc b/lib/air_modes_preamble.cc
index f688a63..8046d78 100644
--- a/lib/air_modes_preamble.cc
+++ b/lib/air_modes_preamble.cc
@@ -29,9 +29,8 @@
 #include <string.h>
 #include <iostream>
 #include <gr_tags.h>
-#include <air_modes_api.h>
 
-AIR_MODES_API air_modes_preamble_sptr air_make_modes_preamble(int channel_rate, float threshold_db)
+air_modes_preamble_sptr air_make_modes_preamble(int channel_rate, float threshold_db)
 {
 	return air_modes_preamble_sptr (new air_modes_preamble(channel_rate, threshold_db));
 }
diff --git a/lib/air_modes_slicer.cc b/lib/air_modes_slicer.cc
index 04c4dd2..1426d56 100644
--- a/lib/air_modes_slicer.cc
+++ b/lib/air_modes_slicer.cc
@@ -32,7 +32,6 @@
 #include <modes_crc.h>
 #include <iostream>
 #include <gr_tags.h>
-#include <air_modes_api.h>
 
 extern "C"
 {
@@ -40,7 +39,7 @@ extern "C"
 #include <string.h>
 }
 
-AIR_MODES_API air_modes_slicer_sptr air_make_modes_slicer(int channel_rate, gr_msg_queue_sptr queue)
+air_modes_slicer_sptr air_make_modes_slicer(int channel_rate, gr_msg_queue_sptr queue)
 {
 	return air_modes_slicer_sptr (new air_modes_slicer(channel_rate, queue));
 }
diff --git a/python/modes_sbs1.py b/python/modes_sbs1.py
index 3f16b13..452d008 100644
--- a/python/modes_sbs1.py
+++ b/python/modes_sbs1.py
@@ -64,8 +64,9 @@ class modes_output_sbs1(modes_parse.modes_parse):
   def output(self, msg):
     try:
       sbs1_msg = self.parse(msg)
-      for conn in self._conns[:]: #iterate over a copy of the list
-        conn.send(sbs1_msg)
+      if sbs1_msg is not None:
+        for conn in self._conns[:]: #iterate over a copy of the list
+          conn.send(sbs1_msg)
     except socket.error:
       self._conns.remove(conn)
       print "Connections: ", len(self._conns)
@@ -145,7 +146,7 @@ class modes_output_sbs1(modes_parse.modes_parse):
   def pp5(self, shortdata, ecc):
     # I'm not sure what to do with the identiifcation shortdata & 0x1FFF
     [datestr, timestr] = self.current_time()
-    [fs, dr, um, ident] = self.parse5(shortdata)
+    [fs, dr, um] = self.parse5(shortdata)
     aircraft_id = self.get_aircraft_id(ecc)
     retstr = "MSG,6,0,%i,%06X,%i,%s,%s,%s,%s,,,,,,,,," % (aircraft_id, ecc, aircraft_id+100, datestr, timestr, datestr, timestr)
     return retstr + self.decode_fs(fs) + "\n"