diff --git a/vcg/space/color4.h b/vcg/space/color4.h
index f9d2b9d0..d97e7480 100644
--- a/vcg/space/color4.h
+++ b/vcg/space/color4.h
@@ -259,8 +259,8 @@ inline static Color4 ColorRamp(const float &minf,const float  &maxf ,float v )
   return rc;
 }
 
-inline static unsigned short ToUnsignedB5G5R5(Color4 &) { return 0;}
-inline static unsigned short ToUnsignedR5G5B5(Color4 &) { return 0;}
+inline static unsigned short ToUnsignedB5G5R5(const Color4 &) { return 0;}
+inline static unsigned short ToUnsignedR5G5B5(const Color4 &) { return 0;}
 
 inline static Color4 FromUnsignedB5G5R5(unsigned short)
 {
@@ -420,7 +420,7 @@ typedef Color4<double>         Color4d;
 
 
 template<>
-inline unsigned short Color4<unsigned char>::ToUnsignedB5G5R5(Color4<unsigned char> &cc)
+inline unsigned short Color4<unsigned char>::ToUnsignedB5G5R5(const Color4<unsigned char> &cc)
 {
   unsigned short r = cc[0]/8;
   unsigned short g = cc[1]/8;
@@ -430,7 +430,7 @@ inline unsigned short Color4<unsigned char>::ToUnsignedB5G5R5(Color4<unsigned ch
 }
 
 template<>
-inline unsigned short Color4<unsigned char>::ToUnsignedR5G5B5(Color4<unsigned char> &cc)
+inline unsigned short Color4<unsigned char>::ToUnsignedR5G5B5(const Color4<unsigned char> &cc)
 {
   unsigned short r = cc[0]/8;
   unsigned short g = cc[1]/8;
diff --git a/wrap/io_trimesh/export_stl.h b/wrap/io_trimesh/export_stl.h
index 50859273..0ed6d9c9 100644
--- a/wrap/io_trimesh/export_stl.h
+++ b/wrap/io_trimesh/export_stl.h
@@ -75,14 +75,14 @@ public:
 typedef typename SaveMeshType::FaceType FaceType;
 typedef unsigned short CallBackSTLFaceAttribute(const SaveMeshType &m, const FaceType &f);
 
-static int Save(SaveMeshType &m, const char * filename, const int &mask, CallBackPos *)
+static int Save(const SaveMeshType &m, const char * filename, const int &mask, CallBackPos *)
 {
  return Save(m,filename,true,mask);
 }
 
-static int Save(SaveMeshType &m, const char * filename , bool binary =true, int mask=0, const char *objectname=0, bool magicsMode=0)
+static int Save(const SaveMeshType &m, const char * filename , bool binary =true, int mask=0, const char *objectname=0, bool magicsMode=0)
 {
-  typedef typename SaveMeshType::FaceIterator FaceIterator;
+  typedef typename SaveMeshType::ConstFaceIterator FaceIterator;
     FILE *fp;
 
     fp = fopen(filename,"wb");