diff --git a/src/libei-device.c b/src/libei-device.c
index 11ac2a2..607160b 100644
--- a/src/libei-device.c
+++ b/src/libei-device.c
@@ -25,6 +25,7 @@
 #include "config.h"
 
 #include <errno.h>
+#include <math.h>
 
 #include "util-bits.h"
 #include "util-macros.h"