--- /n/sources/plan9/sys/src/9/port/segment.c	Thu Jul 22 20:47:18 2010
+++ /sys/src/9/port/segment.c	Wed Feb  3 00:00:00 2016
@@ -484,7 +487,7 @@
 		ns = up->seg[i];
 		if(ns == 0 || ns == s)
 			continue;
-		if(newtop >= ns->base && newtop < ns->top) {
+		if(newtop > ns->base && s->base < ns->top) {
 			qunlock(&s->lk);
 			error(Esoverlap);
 		}
@@ -586,8 +589,7 @@
 		ns = p->seg[i];
 		if(ns == 0)
 			continue;
-		if((newtop > ns->base && newtop <= ns->top) ||
-		   (va >= ns->base && va < ns->top))
+		if(newtop > ns->base && va < ns->top)
 			return ns;
 	}
 	return nil;