diff --git a/include/boost/gil/channel_algorithm.hpp b/include/boost/gil/channel_algorithm.hpp
index 8f112ca8a..20f53dde1 100644
--- a/include/boost/gil/channel_algorithm.hpp
+++ b/include/boost/gil/channel_algorithm.hpp
@@ -329,7 +329,7 @@ template <> struct channel_convert_to_unsigned<bits16s> : public std::unary_func
 
 template <> struct channel_convert_to_unsigned<bits32s> : public std::unary_function<bits32s,bits32> {
     typedef bits32 type;
-    type operator()(bits32s x) const { return static_cast<bits32>(x+(1<<31)); }
+    type operator()(bits32s x) const { return static_cast<bits32>(x)+(1u<<31); }
 };
 
 
@@ -352,7 +352,7 @@ template <> struct channel_convert_from_unsigned<bits16s> : public std::unary_fu
 
 template <> struct channel_convert_from_unsigned<bits32s> : public std::unary_function<bits32,bits32s> {
     typedef bits32s type;
-    type operator()(bits32 x) const { return static_cast<bits32s>(x-(1<<31)); }
+    type operator()(bits32 x) const { return static_cast<bits32s>(x-(1u<<31)); }
 };
 
 }   // namespace detail
diff --git a/include/boost/gil/extension/io/formats/bmp/reader_backend.hpp b/include/boost/gil/extension/io/formats/bmp/reader_backend.hpp
index f7631d5ce..de294996d 100644
--- a/include/boost/gil/extension/io/formats/bmp/reader_backend.hpp
+++ b/include/boost/gil/extension/io/formats/bmp/reader_backend.hpp
@@ -189,7 +189,7 @@ public:
 
         if( entries == 0 )
         {
-            entries = 1 << this->_info._bits_per_pixel;
+            entries = 1u << this->_info._bits_per_pixel;
         }
 
         _palette.resize( entries, rgba8_pixel_t(0, 0, 0, 0));
diff --git a/include/boost/gil/extension/io/formats/bmp/scanline_read.hpp b/include/boost/gil/extension/io/formats/bmp/scanline_read.hpp
index e500c45d2..eaf761e56 100644
--- a/include/boost/gil/extension/io/formats/bmp/scanline_read.hpp
+++ b/include/boost/gil/extension/io/formats/bmp/scanline_read.hpp
@@ -289,7 +289,7 @@ private:
 
         if( entries == 0 )
         {
-            entries = 1 << this->_info._bits_per_pixel;
+            entries = 1u << this->_info._bits_per_pixel;
         }
 
 		this->_palette.resize( entries, rgba8_pixel_t(0,0,0,0) );
diff --git a/include/boost/gil/extension/io/formats/bmp/write.hpp b/include/boost/gil/extension/io/formats/bmp/write.hpp
index 7bdea358c..335dff600 100644
--- a/include/boost/gil/extension/io/formats/bmp/write.hpp
+++ b/include/boost/gil/extension/io/formats/bmp/write.hpp
@@ -111,7 +111,7 @@ private:
         ///        in this context.
         if( bpp <= 8 )
         {
-            entries = 1 << bpp;
+            entries = 1u << bpp;
         }
 */
 
diff --git a/include/boost/gil/extension/io/formats/png/writer_backend.hpp b/include/boost/gil/extension/io/formats/png/writer_backend.hpp
index c5934f6f6..f049f5bdd 100644
--- a/include/boost/gil/extension/io/formats/png/writer_backend.hpp
+++ b/include/boost/gil/extension/io/formats/png/writer_backend.hpp
@@ -355,7 +355,7 @@ protected:
 
         if( _info._valid_transparency_factors )
         {
-            int sample_max = ( 1 << _info._bit_depth );
+            int sample_max = ( 1u << _info._bit_depth );
 
             /* libpng doesn't reject a tRNS chunk with out-of-range samples */
             if( !(  (  _info._color_type == PNG_COLOR_TYPE_GRAY