diff --git a/lib/framework/trig.h b/lib/framework/trig.h
index 0beb2848b..175124e86 100644
--- a/lib/framework/trig.h
+++ b/lib/framework/trig.h
@@ -17,12 +17,16 @@
 	along with Warzone 2100; if not, write to the Free Software
 	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */
-/*! \file trig.h
+/** \file
  *  * \brief Interface to trig lookup tables
  */
+
 #ifndef _trig_h
 #define _trig_h
 
+#include "frame.h"
+#include "math-help.h"
+
 /* The number of units around a full circle */
 #define TRIG_DEGREES	360
 
diff --git a/src/difficulty.c b/src/difficulty.c
index 4905a53c9..f9f48cb1c 100644
--- a/src/difficulty.c
+++ b/src/difficulty.c
@@ -31,6 +31,7 @@
 #include "lib/framework/frame.h"
 
 #include <math.h>
+#include "lib/framework/math-help.h"
 
 #include "difficulty.h"
 // ------------------------------------------------------------------------------------