diff --git a/include/utils/polygonUtils.h b/include/utils/polygonUtils.h
index 59d71a9354..ecda641626 100644
--- a/include/utils/polygonUtils.h
+++ b/include/utils/polygonUtils.h
@@ -207,7 +207,7 @@ class PolygonUtils
      * \param max_dist2 The squared maximal allowed distance from the point to the nearest polygon.
      * \return The index to the polygon onto which we have moved the point.
      */
-    static unsigned int moveInside(const Polygons& polygons, Point2LL& from, int distance = 0, int64_t max_dist2 = std::numeric_limits<int64_t>::max());
+    static size_t moveInside(const Polygons& polygons, Point2LL& from, int distance = 0, int64_t max_dist2 = std::numeric_limits<int64_t>::max());
 
     /**
      * \brief Moves the point \p from onto the nearest polygon or leaves the
diff --git a/src/LayerPlan.cpp b/src/LayerPlan.cpp
index 6077daa44d..7d4ede0d0f 100644
--- a/src/LayerPlan.cpp
+++ b/src/LayerPlan.cpp
@@ -2283,8 +2283,8 @@ bool LayerPlan::writePathWithCoasting(
 
     bool length_is_less_than_min_dist = true;
 
-    unsigned int acc_dist_idx_gt_coast_dist = NO_INDEX; // the index of the first point with accumulated_dist more than coasting_dist (= index into accumulated_dist_per_point)
-                                                        // == the point printed BEFORE the start point for coasting
+    std::optional<size_t> acc_dist_idx_gt_coast_dist; // the index of the first point with accumulated_dist more than coasting_dist (= index into accumulated_dist_per_point)
+                                                      // == the point printed BEFORE the start point for coasting
 
     const Point2LL* last = &path.points[path.points.size() - 1];
     for (unsigned int backward_point_idx = 1; backward_point_idx < path.points.size(); backward_point_idx++)
@@ -2294,7 +2294,7 @@ bool LayerPlan::writePathWithCoasting(
         accumulated_dist += distance;
         accumulated_dist_per_point.push_back(accumulated_dist);
 
-        if (acc_dist_idx_gt_coast_dist == NO_INDEX && accumulated_dist >= coasting_dist)
+        if (! acc_dist_idx_gt_coast_dist.has_value() && accumulated_dist >= coasting_dist)
         {
             acc_dist_idx_gt_coast_dist = backward_point_idx; // the newly added point
         }
@@ -2321,22 +2321,23 @@ bool LayerPlan::writePathWithCoasting(
         {
             return false; // Skip coasting at all then.
         }
-        for (acc_dist_idx_gt_coast_dist = 1; acc_dist_idx_gt_coast_dist < accumulated_dist_per_point.size(); acc_dist_idx_gt_coast_dist++)
+        for (acc_dist_idx_gt_coast_dist = 1; acc_dist_idx_gt_coast_dist.value() < accumulated_dist_per_point.size(); acc_dist_idx_gt_coast_dist.value()++)
         { // search for the correct coast_dist_idx
-            if (accumulated_dist_per_point[acc_dist_idx_gt_coast_dist] >= actual_coasting_dist)
+            if (accumulated_dist_per_point[acc_dist_idx_gt_coast_dist.value()] >= actual_coasting_dist)
             {
                 break;
             }
         }
     }
 
-    assert(acc_dist_idx_gt_coast_dist < accumulated_dist_per_point.size()); // something has gone wrong; coasting_min_dist < coasting_dist ?
+    assert(
+        acc_dist_idx_gt_coast_dist.has_value() && acc_dist_idx_gt_coast_dist < accumulated_dist_per_point.size()); // something has gone wrong; coasting_min_dist < coasting_dist ?
 
-    const size_t point_idx_before_start = path.points.size() - 1 - acc_dist_idx_gt_coast_dist;
+    const size_t point_idx_before_start = path.points.size() - 1 - acc_dist_idx_gt_coast_dist.value();
 
     Point2LL start;
     { // computation of begin point of coasting
-        const coord_t residual_dist = actual_coasting_dist - accumulated_dist_per_point[acc_dist_idx_gt_coast_dist - 1];
+        const coord_t residual_dist = actual_coasting_dist - accumulated_dist_per_point[acc_dist_idx_gt_coast_dist.value() - 1];
         const Point2LL& a = path.points[point_idx_before_start];
         const Point2LL& b = path.points[point_idx_before_start + 1];
         start = b + normal(a - b, residual_dist);
diff --git a/src/utils/polygonUtils.cpp b/src/utils/polygonUtils.cpp
index 42f9204a05..4855f34046 100644
--- a/src/utils/polygonUtils.cpp
+++ b/src/utils/polygonUtils.cpp
@@ -327,13 +327,13 @@ ClosestPolygonPoint PolygonUtils::_moveInside2(const ClosestPolygonPoint& closes
 /*
  * Implementation assumes moving inside, but moving outside should just as well be possible.
  */
-unsigned int PolygonUtils::moveInside(const Polygons& polygons, Point2LL& from, int distance, int64_t maxDist2)
+size_t PolygonUtils::moveInside(const Polygons& polygons, Point2LL& from, int distance, int64_t maxDist2)
 {
     Point2LL ret = from;
     int64_t bestDist2 = std::numeric_limits<int64_t>::max();
-    unsigned int bestPoly = NO_INDEX;
+    size_t bestPoly = NO_INDEX;
     bool is_already_on_correct_side_of_boundary = false; // whether [from] is already on the right side of the boundary
-    for (unsigned int poly_idx = 0; poly_idx < polygons.size(); poly_idx++)
+    for (size_t poly_idx = 0; poly_idx < polygons.size(); poly_idx++)
     {
         ConstPolygonRef poly = polygons[poly_idx];
         if (poly.size() < 2)