diff --git a/configure.ac b/configure.ac
index aba3d82afd..9529dc95ff 100644
--- a/configure.ac
+++ b/configure.ac
@@ -592,7 +592,7 @@ AM_CONDITIONAL(BUILD_UNITTESTS, test x$supports_unittests = xyes)
 # In order to detect support of sendmmsg() and accept4(), we need to escape the POSIX
 # jail by defining _GNU_SOURCE or <sys/socket.h> will not expose it.
 case $host_os in
-  linux*|cygwin*|msys*)
+  *linux*|cygwin*|msys*)
     CPPFLAGS="$CPPFLAGS -D_GNU_SOURCE"
     ;;
 esac