1 files changed, 3 insertions, 1 deletions
diff --git a/src/PJ_mbtfpp.c b/src/PJ_mbtfpp.c
index 9b90444b..5e5b2d50 100644
--- a/src/PJ_mbtfpp.c
+++ b/src/PJ_mbtfpp.c
@@ -1,4 +1,7 @@
 #define PJ_LIB__
+
+#include <math.h>
+
 #include "proj.h"
 #include "projects.h"
 
@@ -60,4 +63,3 @@ PJ *PROJECTION(mbtfpp) {
 
     return P;
 }
-