diff --git a/mcpwm_foc.c b/mcpwm_foc.c
index 48609cf2..4490d14a 100644
--- a/mcpwm_foc.c
+++ b/mcpwm_foc.c
@@ -17,6 +17,8 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
     */
 
+#define _GNU_SOURCE         /* for sincosf */
+
 #include "mcpwm_foc.h"
 #include "mc_interface.h"
 #include "ch.h"