diff --git a/xs/src/libslic3r/Config.hpp b/xs/src/libslic3r/Config.hpp
index 2d192d235..49a14e221 100644
--- a/xs/src/libslic3r/Config.hpp
+++ b/xs/src/libslic3r/Config.hpp
@@ -459,6 +459,7 @@ class ConfigOptionEnumGeneric : public ConfigOption
 };
 
 enum ConfigOptionType {
+    coNone,
     coFloat,
     coFloats,
     coInt,
@@ -500,7 +501,8 @@ class ConfigOptionDef
     std::vector<std::string> enum_labels;
     t_config_enum_values enum_keys_map;
     
-    ConfigOptionDef() : multiline(false), full_width(false), readonly(false),
+    ConfigOptionDef() : type(coNone),
+                        multiline(false), full_width(false), readonly(false),
                         height(-1), width(-1), min(INT_MIN), max(INT_MAX) {};
 };
 
diff --git a/xs/src/libslic3r/Extruder.cpp b/xs/src/libslic3r/Extruder.cpp
index 8cbd00b73..e254d6806 100644
--- a/xs/src/libslic3r/Extruder.cpp
+++ b/xs/src/libslic3r/Extruder.cpp
@@ -2,7 +2,7 @@
 
 namespace Slic3r {
 
-Extruder::Extruder(int id, GCodeConfig *config)
+Extruder::Extruder(unsigned int id, GCodeConfig *config)
 :   id(id),
     config(config)
 {
diff --git a/xs/src/libslic3r/Extruder.hpp b/xs/src/libslic3r/Extruder.hpp
index 03ee7c57f..fa91bb42f 100644
--- a/xs/src/libslic3r/Extruder.hpp
+++ b/xs/src/libslic3r/Extruder.hpp
@@ -10,7 +10,7 @@ namespace Slic3r {
 class Extruder
 {
     public:
-    int id;
+    unsigned int id;
     double E;
     double absolute_E;
     double retracted;
@@ -18,7 +18,7 @@ class Extruder
     double e_per_mm3;
     double retract_speed_mm_min;
     
-    Extruder(int id, GCodeConfig *config);
+    Extruder(unsigned int id, GCodeConfig *config);
     virtual ~Extruder() {}
     void reset();
     double extrude(double dE);
diff --git a/xs/src/libslic3r/ExtrusionEntity.cpp b/xs/src/libslic3r/ExtrusionEntity.cpp
index 846269185..be32519f6 100644
--- a/xs/src/libslic3r/ExtrusionEntity.cpp
+++ b/xs/src/libslic3r/ExtrusionEntity.cpp
@@ -283,7 +283,7 @@ ExtrusionLoop::has_overhang_point(const Point &point) const
         if (pos != -1) {
             // point belongs to this path
             // we consider it overhang only if it's not an endpoint
-            return (path->is_bridge() && pos > 0 && pos != path->polyline.points.size()-1);
+            return (path->is_bridge() && pos > 0 && pos != (int)(path->polyline.points.size())-1);
         }
     }
     return false;
diff --git a/xs/src/libslic3r/MotionPlanner.cpp b/xs/src/libslic3r/MotionPlanner.cpp
index f8e7d1dd9..d35a89ec5 100644
--- a/xs/src/libslic3r/MotionPlanner.cpp
+++ b/xs/src/libslic3r/MotionPlanner.cpp
@@ -73,7 +73,7 @@ MotionPlanner::initialize()
 }
 
 ExPolygonCollection
-MotionPlanner::get_env(size_t island_idx) const
+MotionPlanner::get_env(int island_idx) const
 {
     if (island_idx == -1) {
         return ExPolygonCollection(this->outer);
diff --git a/xs/src/libslic3r/MotionPlanner.hpp b/xs/src/libslic3r/MotionPlanner.hpp
index 608f01681..d49cc8198 100644
--- a/xs/src/libslic3r/MotionPlanner.hpp
+++ b/xs/src/libslic3r/MotionPlanner.hpp
@@ -33,7 +33,7 @@ class MotionPlanner
     
     void initialize();
     MotionPlannerGraph* init_graph(int island_idx);
-    ExPolygonCollection get_env(size_t island_idx) const;
+    ExPolygonCollection get_env(int island_idx) const;
     Point nearest_env_point(const ExPolygonCollection &env, const Point &from, const Point &to) const;
 };
 
@@ -42,7 +42,7 @@ class MotionPlannerGraph
     friend class MotionPlanner;
     
     private:
-    typedef size_t node_t;
+    typedef int node_t;
     typedef double weight_t;
     struct neighbor {
         node_t target;
diff --git a/xs/xsp/Extruder.xsp b/xs/xsp/Extruder.xsp
index c244e02e4..aac39c413 100644
--- a/xs/xsp/Extruder.xsp
+++ b/xs/xsp/Extruder.xsp
@@ -6,7 +6,7 @@
 %}
 
 %name{Slic3r::Extruder} class Extruder {
-    Extruder(int id, GCodeConfig *config);
+    Extruder(unsigned int id, GCodeConfig *config);
     ~Extruder();
     void reset();
     double extrude(double dE);
@@ -16,7 +16,7 @@
     double extruded_volume();
     double used_filament();
     
-    int id()
+    unsigned int id()
         %code%{ RETVAL = THIS->id; %};
     
     double E()