diff --git a/src/Mod/PartDesign/App/FeaturePocket.cpp b/src/Mod/PartDesign/App/FeaturePocket.cpp
index 43e07b69a..e111a0723 100644
--- a/src/Mod/PartDesign/App/FeaturePocket.cpp
+++ b/src/Mod/PartDesign/App/FeaturePocket.cpp
@@ -153,8 +153,12 @@ App::DocumentObjectExecReturn *Pocket::execute(void)
             }
             getUpToFace(upToFace, base, supportface, sketchshape, method, dir, Offset.getValue());
 
-            // Special treatment because often the created stand-alone prism is invalid (empty) because
-            // BRepFeat_MakePrism(..., 2, 1) is buggy
+            // BRepFeat_MakePrism(..., 2, 1) in combination with PerForm(upToFace) is buggy when the
+            // prism that is being created is contained completely inside the base solid
+            // In this case the resulting shape is empty. This is not a problem for the Pad or Pocket itself
+            // but it leads to an invalid SubShape
+            // The bug only occurs when the upToFace is limited (by a wire), not for unlimited upToFace. But
+            // other problems occur with unlimited concave upToFace so it is not an option to always unlimit upToFace
             // Check supportface for limits, otherwise Perform() throws an exception
             TopExp_Explorer Ex(supportface,TopAbs_WIRE);
             if (!Ex.More())
diff --git a/src/Mod/PartDesign/App/FeatureSketchBased.cpp b/src/Mod/PartDesign/App/FeatureSketchBased.cpp
index b5f3633b6..b3604a45a 100644
--- a/src/Mod/PartDesign/App/FeatureSketchBased.cpp
+++ b/src/Mod/PartDesign/App/FeatureSketchBased.cpp
@@ -628,8 +628,10 @@ void SketchBased::generatePrism(TopoDS_Shape& prism,
 const bool SketchBased::checkWireInsideFace(const TopoDS_Wire& wire, const TopoDS_Face& face,
                                             const gp_Dir& dir) {
     // Project wire onto the face (face, not surface! So limits of face apply)
-    // FIXME: For a user-selected upToFace, sometimes this returns a non-closed wire for no apparent reason
-    // Check again after introduction of "robust" reference for upToFace
+    // FIXME: The results of BRepProj_Projection do not seem to be very stable. Sometimes they return no result
+    // even in the simplest projection case.
+    // FIXME: Checking for Closed() is wrong because this has nothing to do with the wire itself being closed
+    // But ShapeAnalysis_Wire::CheckClosed() doesn't give correct results either.
     BRepProj_Projection proj(wire, face, dir);
     return (proj.More() && proj.Current().Closed());
 }