1 files changed, 3 insertions, 1 deletions
diff --git a/src/proj_rouss.c b/src/proj_rouss.c
index bbf6ff0f..ca4476bb 100644
--- a/src/proj_rouss.c
+++ b/src/proj_rouss.c
@@ -24,7 +24,10 @@
 ** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 #define PJ_LIB__
+
 #include <errno.h>
+#include <math.h>
+
 #include "proj.h"
 #include "projects.h"
 
@@ -151,4 +154,3 @@ PJ *PROJECTION(rouss) {
 
     return P;
 }
-