diff --git a/src/libslic3r/Polyline.cpp b/src/libslic3r/Polyline.cpp
index d805473b58e..5743e38bd5b 100644
--- a/src/libslic3r/Polyline.cpp
+++ b/src/libslic3r/Polyline.cpp
@@ -267,29 +267,34 @@ ThickLines ThickPolyline::thicklines() const
 // Removes the given distance from the end of the ThickPolyline
 void ThickPolyline::clip_end(double distance)
 {
-    while (distance > 0) {
-        Vec2d    last_point = this->last_point().cast<double>();
-        coordf_t last_width = this->width.back();
-        this->points.pop_back();
-        this->width.pop_back();
-        if (this->points.empty())
-            break;
-
-        Vec2d    vec            = this->last_point().cast<double>() - last_point;
-        coordf_t width_diff     = this->width.back() - last_width;
-        double   vec_length_sqr = vec.squaredNorm();
-        if (vec_length_sqr > distance * distance) {
-            double t = (distance / std::sqrt(vec_length_sqr));
-            this->points.emplace_back((last_point + vec * t).cast<coord_t>());
-            this->width.emplace_back(last_width + width_diff * t);
-            assert(this->width.size() == (this->points.size() - 1) * 2);
-            return;
-        } else
+    if (! this->empty()) {
+        assert(this->width.size() == (this->points.size() - 1) * 2);
+        while (distance > 0) {
+            Vec2d last_point = this->last_point().cast<double>();
+            this->points.pop_back();
+            if (this->points.empty()) {
+                assert(this->width.empty());
+                break;
+            }
+            coordf_t last_width = this->width.back();
             this->width.pop_back();
 
-        distance -= std::sqrt(vec_length_sqr);
+            Vec2d    vec            = this->last_point().cast<double>() - last_point;
+            coordf_t width_diff     = this->width.back() - last_width;
+            double   vec_length_sqr = vec.squaredNorm();
+            if (vec_length_sqr > distance * distance) {
+                double t = (distance / std::sqrt(vec_length_sqr));
+                this->points.emplace_back((last_point + vec * t).cast<coord_t>());
+                this->width.emplace_back(last_width + width_diff * t);
+                assert(this->width.size() == (this->points.size() - 1) * 2);
+                return;
+            } else
+                this->width.pop_back();
+
+            distance -= std::sqrt(vec_length_sqr);
+        }
     }
-    assert(this->width.size() == (this->points.size() - 1) * 2);
+    assert(this->points.empty() ? this->width.empty() : this->width.size() == (this->points.size() - 1) * 2);
 }
 
 void ThickPolyline::start_at_index(int index)
diff --git a/src/libslic3r/Polyline.hpp b/src/libslic3r/Polyline.hpp
index 8e362f03719..1b23388e184 100644
--- a/src/libslic3r/Polyline.hpp
+++ b/src/libslic3r/Polyline.hpp
@@ -187,6 +187,7 @@ struct ThickPolyline {
     const Point& last_point()   const { return this->points.back(); }
     size_t       size()         const { return this->points.size(); }
     bool         is_valid()     const { return this->points.size() >= 2; }
+    bool         empty()        const { return this->points.empty(); }
     double       length()       const { return Slic3r::length(this->points); }
 
     void         clear() { this->points.clear(); this->width.clear(); }