diff --git a/gtk/conf.c b/gtk/conf.c
index 24b124465..49d81a09d 100644
--- a/gtk/conf.c
+++ b/gtk/conf.c
@@ -36,7 +36,6 @@
 
 #include <libtransmission/transmission.h>
 #include <libtransmission/bencode.h>
-#include <libtransmission/platform.h>
 
 #include "conf.h"
 #include "tr-prefs.h"
diff --git a/libtransmission/JSON_parser.h b/libtransmission/JSON_parser.h
index c18fa9007..bddd6e014 100644
--- a/libtransmission/JSON_parser.h
+++ b/libtransmission/JSON_parser.h
@@ -1,3 +1,7 @@
+#ifndef __TRANSMISSION__
+#error only libtransmission should #include this header.
+#endif
+
 #ifndef JSON_PARSER_H
 #define JSON_PARSER_H
 
diff --git a/libtransmission/clients.h b/libtransmission/clients.h
index 8284888af..eda212f24 100644
--- a/libtransmission/clients.h
+++ b/libtransmission/clients.h
@@ -10,10 +10,16 @@
  * $Id$
  */
 
+#ifndef __TRANSMISSION__
+ #error only libtransmission should #include this header.
+#endif
+
+#ifndef TR_CLIENTS_H
+#define TR_CLIENTS_H
+
 /**
  * @ingroup utils
  */
-void tr_clientForId( char       * buf,
-                     size_t       buflen,
-                     const void * peer_id );
+void tr_clientForId( char * buf, size_t buflen, const void * peer_id );
 
+#endif
diff --git a/libtransmission/platform.h b/libtransmission/platform.h
index 02cfd0051..2824f1e88 100644
--- a/libtransmission/platform.h
+++ b/libtransmission/platform.h
@@ -13,6 +13,10 @@
 #ifndef TR_PLATFORM_H
 #define TR_PLATFORM_H
 
+#ifndef __TRANSMISSION__
+ #error only libtransmission should #include this header.
+#endif
+
 #if defined( WIN32 )
  #define TR_PATH_DELIMITER '\\'
  #define TR_PATH_DELIMITER_STR "\\"
diff --git a/libtransmission/tr-dht.h b/libtransmission/tr-dht.h
index 568115a88..fce2ac0d1 100644
--- a/libtransmission/tr-dht.h
+++ b/libtransmission/tr-dht.h
@@ -20,11 +20,18 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
-#define TR_DHT_STOPPED 0
-#define TR_DHT_BROKEN 1
-#define TR_DHT_POOR 2
-#define TR_DHT_FIREWALLED 3
-#define TR_DHT_GOOD 4
+#ifndef __TRANSMISSION__
+ #error only libtransmission should #include this header.
+#endif
+
+enum
+{
+    TR_DHT_STOPPED      = 0,
+    TR_DHT_BROKEN       = 1,
+    TR_DHT_POOR         = 2,
+    TR_DHT_FIREWALLED   = 3,
+    TR_DHT_GOOD         = 4
+};
 
 int  tr_dhtInit( tr_session *, const tr_address * );
 void tr_dhtUninit( tr_session * );