diff --git a/src/libslic3r/GCode/ToolOrdering.cpp b/src/libslic3r/GCode/ToolOrdering.cpp
index 011420e71..43f498b60 100644
--- a/src/libslic3r/GCode/ToolOrdering.cpp
+++ b/src/libslic3r/GCode/ToolOrdering.cpp
@@ -355,7 +355,7 @@ void ToolOrdering::fill_wipe_tower_partitions(const PrintConfig &config, coordf_
         max_layer_height = std::min(max_layer_height, mlh);
     }
     // The Prusa3D Fast (0.35mm layer height) print profile sets a higher layer height than what is normally allowed
-    // by the nozzle. This is a hack and it works by increasing extrusion width.
+    // by the nozzle. This is a hack and it works by increasing extrusion width. See GH #3919.
     max_layer_height = std::max(max_layer_height, max_object_layer_height);
 
     for (size_t i = 0; i + 1 < m_layer_tools.size(); ++ i) {
@@ -400,47 +400,21 @@ void ToolOrdering::fill_wipe_tower_partitions(const PrintConfig &config, coordf_
     // and maybe other problems. We will therefore go through layer_tools and detect and fix this.
     // So, if there is a non-object layer starting with different extruder than the last one ended with (or containing more than one extruder),
     // we'll mark it with has_wipe tower.
-    assert(! m_layer_tools.empty() && m_layer_tools.front().has_wipe_tower);
-    if (! m_layer_tools.empty() && m_layer_tools.front().has_wipe_tower) {
-        for (size_t i = 0; i + 1 < m_layer_tools.size();) {
-            const LayerTools &lt = m_layer_tools[i];
-            assert(lt.has_wipe_tower);
-            assert(! lt.extruders.empty());
-            // Find the next layer with wipe tower or mark a layer as such.
-            size_t j = i + 1;
-            for (; j < m_layer_tools.size() && ! m_layer_tools[j].has_wipe_tower; ++ j) {
-                LayerTools &lt_next = m_layer_tools[j];
-                if (lt_next.extruders.empty()) {
-                    //FIXME Vojtech: Lukasi, proc?
-                    j = m_layer_tools.size();
-                    break;
-                }
-                if (lt_next.extruders.front() != lt.extruders.back() || lt_next.extruders.size() > 1) {
-                    // Support only layer, soluble layers? Otherwise the layer should have been already marked as having wipe tower.
-                    assert(lt_next.has_support && ! lt_next.has_object);
-                    lt_next.has_wipe_tower = true;
-                    break;
-                }
+    for (unsigned int i=0; i+1<m_layer_tools.size(); ++i) {
+        LayerTools& lt = m_layer_tools[i];
+        LayerTools& lt_next = m_layer_tools[i+1];
+        if (lt.extruders.empty() || lt_next.extruders.empty())
+            break;
+        if (!lt_next.has_wipe_tower && (lt_next.extruders.front() != lt.extruders.back() || lt_next.extruders.size() > 1))
+            lt_next.has_wipe_tower = true;
+        // We should also check that the next wipe tower layer is no further than max_layer_height:
+        unsigned int j = i+1;
+        double last_wipe_tower_print_z = lt_next.print_z;
+        while (++j < m_layer_tools.size()-1 && !m_layer_tools[j].has_wipe_tower)
+            if (m_layer_tools[j+1].print_z - last_wipe_tower_print_z > max_layer_height + EPSILON) {
+                m_layer_tools[j].has_wipe_tower = true;
+                last_wipe_tower_print_z = m_layer_tools[j].print_z;
             }
-            if (j == m_layer_tools.size())
-                // No wipe tower above layer i, therefore no need to add any wipe tower layer above i.
-                break;
-            // We should also check that the next wipe tower layer is no further than max_layer_height.
-            // This algorith may in theory create very thin wipe layer j if layer closely below j is marked as wipe tower.
-            // This may happen if printing with non-soluble break away supports.
-            // On the other side it should not hurt as there will be no wipe, just perimeter and sparse infill printed
-            // at that particular wipe tower layer without extruder change.
-            double last_wipe_tower_print_z = lt.print_z;
-            assert(m_layer_tools[j].has_wipe_tower);
-            for (size_t k = i + 1; k < j; ++k) {
-                assert(! m_layer_tools[k].has_wipe_tower);
-                if (m_layer_tools[k + 1].print_z - last_wipe_tower_print_z > max_layer_height + EPSILON) {
-                    m_layer_tools[k].has_wipe_tower = true;
-                    last_wipe_tower_print_z = m_layer_tools[k].print_z;
-                }
-            }
-            i = j;
-        }
     }
 
     // Calculate the wipe_tower_layer_height values.
diff --git a/src/slic3r/GUI/GUI_ObjectList.hpp b/src/slic3r/GUI/GUI_ObjectList.hpp
index ad222a4a8..aa5264b07 100644
--- a/src/slic3r/GUI/GUI_ObjectList.hpp
+++ b/src/slic3r/GUI/GUI_ObjectList.hpp
@@ -13,6 +13,8 @@
 #include "wxExtensions.hpp"
 #include "ObjectDataViewModel.hpp"
 
+#include "libslic3r/PrintConfig.hpp"
+
 class wxBoxSizer;
 class wxBitmapComboBox;
 class wxMenuItem;