c3-lang/libbsd

diff --git a/configure.ac b/configure.ac
index 55fcfe6..7769182 100644
--- a/configure.ac
+++ b/configure.ac
@@ -59,7 +59,7 @@ AS_CASE([$host_os],
 )
 
 # Checks for header files.
-AC_CHECK_HEADERS([sys/ndir.h sys/dir.h ndir.h dirent.h])
+AC_CHECK_HEADERS([sys/ndir.h sys/dir.h ndir.h dirent.h grp.h])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_INLINE
diff --git a/test/overlay.c b/test/overlay.c
index 7812fcc..a17904f 100644
--- a/test/overlay.c
+++ b/test/overlay.c
@@ -28,7 +28,9 @@
  * other headers through magic macros, to check that the overlay is working
  * properly. */
 #include <errno.h>
+#ifdef HAVE_GRP_H
 #include <grp.h>
+#endif
 #include <stdint.h>
 
 /* Include libbsd overlayed headers that might get partially included. */