diff --git a/openbsc/src/gprs/oap.c b/openbsc/src/gprs/oap.c
index f5d7a95..eb0dd19 100644
--- a/openbsc/src/gprs/oap.c
+++ b/openbsc/src/gprs/oap.c
@@ -20,6 +20,8 @@
  *
  */
 
+#include <string.h>
+
 #include <osmocom/core/utils.h>
 #include <osmocom/crypt/auth.h>