diff --git a/libopenjpeg/tcd.c b/libopenjpeg/tcd.c
index 18cdbc78..94c5d79f 100644
--- a/libopenjpeg/tcd.c
+++ b/libopenjpeg/tcd.c
@@ -30,6 +30,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define _ISOC99_SOURCE /* lrintf is C99 */
 #include "opj_includes.h"
 
 void tcd_dump(FILE *fd, opj_tcd_t *tcd, opj_tcd_image_t * img) {