diff --git a/src/libslic3r/SLA/SLASupportTreeBuilder.cpp b/src/libslic3r/SLA/SLASupportTreeBuilder.cpp
index 3fa9f3b984..2e0310ed8d 100644
--- a/src/libslic3r/SLA/SLASupportTreeBuilder.cpp
+++ b/src/libslic3r/SLA/SLASupportTreeBuilder.cpp
@@ -171,6 +171,9 @@ Head::Head(double       r_big_mm,
     , width_mm(length_mm)
     , penetration_mm(penetration)
 {
+    assert(width_mm > 0.);
+    assert(r_back_mm > 0.);
+    assert(r_pin_mm > 0.);
     
     // We create two spheres which will be connected with a robe that fits
     // both circles perfectly.
diff --git a/src/libslic3r/SLA/SLASupportTreeBuilder.hpp b/src/libslic3r/SLA/SLASupportTreeBuilder.hpp
index 95fcdcc326..c0d9f04c0f 100644
--- a/src/libslic3r/SLA/SLASupportTreeBuilder.hpp
+++ b/src/libslic3r/SLA/SLASupportTreeBuilder.hpp
@@ -311,7 +311,7 @@ public:
         if (m_pillars.capacity() < m_heads.size())
             m_pillars.reserve(m_heads.size() * 10);
         
-        assert(headid >= 0 && headid < m_head_indices.size());
+        assert(headid >= 0 && size_t(headid) < m_head_indices.size());
         Head &head = m_heads[m_head_indices[size_t(headid)]];
         
         m_pillars.emplace_back(head, std::forward<Args>(args)...);
@@ -328,7 +328,7 @@ public:
     void add_pillar_base(long pid, double baseheight = 3, double radius = 2)
     {
         std::lock_guard<Mutex> lk(m_mutex);
-        assert(pid >= 0 && pid < m_pillars.size());
+        assert(pid >= 0 && size_t(pid) < m_pillars.size());
         m_pillars[size_t(pid)].add_base(baseheight, radius);
     }
     
@@ -398,7 +398,7 @@ public:
     const Bridge& add_bridge(long headid, const Vec3d &endp, size_t s = 45)
     {
         std::lock_guard<Mutex> lk(m_mutex);
-        assert(headid >= 0 && headid < m_head_indices.size());
+        assert(headid >= 0 && size_t(headid) < m_head_indices.size());
         
         Head &h = m_heads[m_head_indices[size_t(headid)]];
         m_bridges.emplace_back(h.junction_point(), endp, h.r_back_mm, s);
diff --git a/src/libslic3r/SLA/SLASupportTreeBuildsteps.cpp b/src/libslic3r/SLA/SLASupportTreeBuildsteps.cpp
index 60e8f15b79..392a963e12 100644
--- a/src/libslic3r/SLA/SLASupportTreeBuildsteps.cpp
+++ b/src/libslic3r/SLA/SLASupportTreeBuildsteps.cpp
@@ -1096,6 +1096,11 @@ void SupportTreeBuildsteps::routing_to_model()
             double dist = distance(endp, hitp) + m_cfg.head_penetration_mm;
             double w = dist - 2 * head.r_pin_mm - head.r_back_mm;
             
+            if (w < 0.) {
+                BOOST_LOG_TRIVIAL(error) << "Pinhead width is negative!";
+                w = 0.;
+            }
+                
             Head tailhead(head.r_back_mm,
                           head.r_pin_mm,
                           w,
@@ -1348,7 +1353,7 @@ void SupportTreeBuildsteps::routing_headless()
         m_thr();
         
         const auto R = double(m_support_pts[i].head_front_radius);
-        const double HWIDTH_MM = R/3;
+        const double HWIDTH_MM = m_cfg.head_penetration_mm;
         
         // Exact support position
         Vec3d sph = m_support_pts[i].pos.cast<double>();
diff --git a/tests/sla_print/sla_print_tests_main.cpp b/tests/sla_print/sla_print_tests_main.cpp
index 5952e55454..bd2475f411 100644
--- a/tests/sla_print/sla_print_tests_main.cpp
+++ b/tests/sla_print/sla_print_tests_main.cpp
@@ -260,7 +260,7 @@ void test_support_model_collision(
 
     // Set head penetration to a small negative value which should ensure that
     // the supports will not touch the model body.
-    supportcfg.head_penetration_mm = -1.; // 1 mm should be more than enough
+    supportcfg.head_penetration_mm = -0.1;
 
     test_supports(obj_filename, supportcfg, byproducts);
 
@@ -277,6 +277,7 @@ void test_support_model_collision(
         const ExPolygons &mod_slice = byproducts.model_slices[n];
 
         Polygons intersections = intersection(sup_slice, mod_slice);
+        
         notouch = notouch && intersections.empty();
     }