diff --git a/src/aclocal.m4 b/src/aclocal.m4
index 2c092f410..75727f554 100644
--- a/src/aclocal.m4
+++ b/src/aclocal.m4
@@ -283,6 +283,7 @@ case "${host_os}" in
 		LDRPATH='-Wl,-R,~A'
 		TCPLIBS='-lsocket -lnsl -lintl'
 		clibs='-ldl'
+		CFLAGS="${CFLAGS} -std=gnu99"
 		;;
 	cygwin*)
 		thehost='cygwin'
diff --git a/src/configure b/src/configure
index b61c1d0e0..ed642b33a 100755
--- a/src/configure
+++ b/src/configure
@@ -4450,6 +4450,7 @@ case "${host_os}" in
 		LDRPATH='-Wl,-R,~A'
 		TCPLIBS='-lsocket -lnsl -lintl'
 		clibs='-ldl'
+		CFLAGS="${CFLAGS} -std=gnu99"
 		;;
 	cygwin*)
 		thehost='cygwin'