diff --git a/changelog.txt b/changelog.txt
index 24ba90ad..322757e7 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -2,6 +2,7 @@ Unreleased
 
 * qbsp: fixed surface edge corruption when using skip surfaces
 * qbsp: added "-noskip" option for troubleshooting skip related problems
+* vis: fix portal stack corruption in ClipStackWinding
 * bsputil: added a "--check" option to check internal data consistency
 
 2013-04-10 TyrUtils v0.7
diff --git a/vis/vis.c b/vis/vis.c
index 64480539..d79af645 100644
--- a/vis/vis.c
+++ b/vis/vis.c
@@ -308,6 +308,13 @@ ClipStackWinding(winding_t *in, pstack_t *stack, plane_t *split)
 	if (sides[i + 1] == SIDE_ON || sides[i + 1] == sides[i])
 	    continue;
 
+	if (neww->numpoints == MAX_WINDING_FIXED) {
+	    /* Can't clip, fall back to original */
+	    FreeStackWinding(neww, stack);
+	    c_noclip++;
+	    return in;
+	}
+
 	// generate a split point
 	p2 = in->points[(i + 1) % in->numpoints];