diff --git a/common/polylib.cc b/common/polylib.cc
index 409237f6..6397b310 100644
--- a/common/polylib.cc
+++ b/common/polylib.cc
@@ -223,6 +223,10 @@ polylib::BaseWindingForPlane(const vec3_t normal, const float dist)
 polylib::winding_t *
 polylib::CopyWinding(const winding_t * w)
 {
+    if (w == nullptr) {
+        return nullptr;
+    }
+    
     int size;
     winding_t *c;
 
diff --git a/include/common/bspfile.hh b/include/common/bspfile.hh
index e7dad3f1..01bd23c6 100644
--- a/include/common/bspfile.hh
+++ b/include/common/bspfile.hh
@@ -402,7 +402,7 @@ typedef struct {
 
 typedef struct {
     int32_t planenum;
-    int32_t side;
+    int32_t side;               // if true, the face is on the back side of the plane
     int32_t firstedge;          /* we must support > 64k edges */
     int32_t numedges;
     int32_t texinfo;