diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -516,8 +516,7 @@
 		tfb = NULL;
 	}
 	/* Does the stack accept this connection? */
-	if (tfb != NULL && tfb->tfb_tcp_handoff_ok != NULL &&
-	    (*tfb->tfb_tcp_handoff_ok)(tp)) {
+	if (tfb != NULL && (*tfb->tfb_tcp_handoff_ok)(tp)) {
 		refcount_release(&tfb->tfb_refcnt);
 		tfb = NULL;
 	}
@@ -551,11 +550,9 @@
 		/* there always should be a default */
 		panic("Can't refer to tcp_def_funcblk");
 	}
-	if (tfb->tfb_tcp_handoff_ok != NULL) {
-		if ((*tfb->tfb_tcp_handoff_ok) (tp)) {
-			/* The default stack cannot say no */
-			panic("Default stack rejects a new session?");
-		}
+	if ((*tfb->tfb_tcp_handoff_ok)(tp)) {
+		/* The default stack cannot say no */
+		panic("Default stack rejects a new session?");
 	}
 	if (tfb->tfb_tcp_fb_init != NULL &&
 	    (*tfb->tfb_tcp_fb_init)(tp, &ptr)) {
@@ -1186,6 +1183,7 @@
 	if ((blk->tfb_tcp_output == NULL) ||
 	    (blk->tfb_tcp_do_segment == NULL) ||
 	    (blk->tfb_tcp_ctloutput == NULL) ||
+	    (blk->tfb_tcp_handoff_ok == NULL) ||
 	    (strlen(blk->tfb_tcp_block_name) == 0)) {
 		/*
 		 * These functions are required and you
diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -1742,26 +1742,11 @@
 			INP_WUNLOCK(inp);
 			return (0);
 		}
-		if (tp->t_state != TCPS_CLOSED) {
-			/*
-			 * The user has advanced the state
-			 * past the initial point, we may not
-			 * be able to switch.
-			 */
-			if (blk->tfb_tcp_handoff_ok != NULL) {
-				/*
-				 * Does the stack provide a
-				 * query mechanism, if so it may
-				 * still be possible?
-				 */
-				error = (*blk->tfb_tcp_handoff_ok)(tp);
-			} else
-				error = EINVAL;
-			if (error) {
-				refcount_release(&blk->tfb_refcnt);
-				INP_WUNLOCK(inp);
-				return(error);
-			}
+		error = (*blk->tfb_tcp_handoff_ok)(tp);
+		if (error) {
+			refcount_release(&blk->tfb_refcnt);
+			INP_WUNLOCK(inp);
+			return (error);
 		}
 		if (blk->tfb_flags & TCP_FUNC_BEING_REMOVED) {
 			refcount_release(&blk->tfb_refcnt);
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -542,13 +542,10 @@
 #define	TCP_FUNC_OUTPUT_CANDROP	0x02   	/* tfb_tcp_output may ask tcp_drop */
 
 /**
- * Adding a tfb_tcp_handoff_ok function allows the socket
- * option to change stacks to query you even if the
- * connection is in a later stage. You return 0 to
- * say you can take over and run your stack, you return
- * non-zero (an error number) to say no you can't.
- * If the function is undefined you can only change
- * in the early states (before connect or listen).
+ * tfb_tcp_handoff_ok is a mandatory function allowing
+ * to query a stack, if it can take over a tcpcb.
+ * You return 0 to say you can take over and run your stack,
+ * you return non-zero (an error number) to say no you can't.
  *
  * tfb_tcp_fb_init is used to allow the new stack to
  * setup its control block. Among the things it must