diff --git a/include/haproxy/sock_inet.h b/include/haproxy/sock_inet.h
index 48b23b3..6e3718a 100644
--- a/include/haproxy/sock_inet.h
+++ b/include/haproxy/sock_inet.h
@@ -27,6 +27,8 @@
 
 #include <haproxy/api.h>
 
+extern int sock_inet6_v6only_default;
+
 int sock_inet4_addrcmp(const struct sockaddr_storage *a, const struct sockaddr_storage *b);
 int sock_inet6_addrcmp(const struct sockaddr_storage *a, const struct sockaddr_storage *b);
 int sock_inet_get_dst(int fd, struct sockaddr *sa, socklen_t salen, int dir);
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index fba6083..144f4bc 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -107,11 +107,6 @@
 static THREAD_LOCAL int default_tcp6_maxseg = -1;
 #endif
 
-/* determine if the operating system uses IPV6_V6ONLY by default.
- * -1=unknown, 0=no, 1=yes.
- */
-static int v6only_default = -1;
-
 /* Binds ipv4/ipv6 address <local> to socket <fd>, unless <flags> is set, in which
  * case we try to bind <remote>. <flags> is a 2-bit field consisting of :
  *  - 0 : ignore remote address (may even be a NULL pointer)
@@ -581,32 +576,6 @@
 	return SF_ERR_NONE;  /* connection is OK */
 }
 
-/* sets the v6only_default flag according to the OS' default settings; for
- * simplicity it's set to zero if not supported.
- */
-static inline void tcp_test_v6only_default()
-{
-	if (v6only_default == -1) {
-#if defined(IPV6_V6ONLY)
-		int fd, val;
-		socklen_t len = sizeof(val);
-
-		v6only_default = 0;
-
-		fd = socket(AF_INET6, SOCK_STREAM, 0);
-		if (fd < 0)
-			return;
-
-		if (getsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, &len) == 0 && val > 0)
-			v6only_default = 1;
-
-		close(fd);
-#else
-		v6only_default = 0;
-#endif
-	}
-}
-
 #define LI_MANDATORY_FLAGS	(LI_O_FOREIGN | LI_O_V6ONLY)
 /* When binding the listeners, check if a socket has been sent to us by the
  * previous process that we could reuse, instead of creating a new one.
@@ -617,15 +586,13 @@
 	int options = l->options & (LI_MANDATORY_FLAGS | LI_O_V4V6);
 	int ret = -1;
 
-	tcp_test_v6only_default();
-
 	/* Prepare to match the v6only option against what we really want. Note
 	 * that sadly the two options are not exclusive to each other and that
 	 * v6only is stronger than v4v6.
 	 */
-	if ((options & LI_O_V6ONLY) || (v6only_default && !(options & LI_O_V4V6)))
+	if ((options & LI_O_V6ONLY) || (sock_inet6_v6only_default && !(options & LI_O_V4V6)))
 		options |= LI_O_V6ONLY;
-	else if ((options & LI_O_V4V6) || !v6only_default)
+	else if ((options & LI_O_V4V6) || !sock_inet6_v6only_default)
 		options &= ~LI_O_V6ONLY;
 	options &= ~LI_O_V4V6;
 
diff --git a/src/sock_inet.c b/src/sock_inet.c
index db1a8c0..c5b80da 100644
--- a/src/sock_inet.c
+++ b/src/sock_inet.c
@@ -35,6 +35,10 @@
  * mentioned in the comment before the function definition.
  */
 
+/* determine if the operating system uses IPV6_V6ONLY by default. 0=no, 1=yes.
+ * It also remains if IPv6 is not enabled/configured.
+ */
+int sock_inet6_v6only_default = 0;
 
 /* Compares two AF_INET sockaddr addresses. Returns 0 if they match or non-zero
  * if they do not match.
@@ -165,3 +169,22 @@
 	}
 	return 0;
 }
+
+static void sock_inet_prepare()
+{
+	int fd, val;
+	socklen_t len;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd >= 0) {
+#if defined(IPV6_V6ONLY)
+		/* retrieve the OS' bindv6only value */
+		len = sizeof(val);
+		if (getsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, &len) == 0 && val > 0)
+			sock_inet6_v6only_default = 1;
+#endif
+		close(fd);
+	}
+}
+
+INITCALL0(STG_PREPARE, sock_inet_prepare);