1 files changed, 3 insertions, 1 deletions
diff --git a/src/PJ_hammer.c b/src/PJ_hammer.c
index e7546ac0..f3e0d64e 100644
--- a/src/PJ_hammer.c
+++ b/src/PJ_hammer.c
@@ -1,5 +1,8 @@
 #define PJ_LIB__
+
 #include <errno.h>
+#include <math.h>
+
 #include "proj.h"
 #include "projects.h"
 
@@ -70,4 +73,3 @@ PJ *PROJECTION(hammer) {
 
     return P;
 }
-