diff --git a/dlib/image_loader/jpeg_loader.cpp b/dlib/image_loader/jpeg_loader.cpp
index b28bdf9ea..b1d44c7a4 100644
--- a/dlib/image_loader/jpeg_loader.cpp
+++ b/dlib/image_loader/jpeg_loader.cpp
@@ -182,7 +182,7 @@ namespace dlib
         data.resize(height_*width_*output_components_);
 
         // setup pointers to each row
-        for (unsigned long i = 0; i < rows.size(); ++i)
+        for (size_t i = 0; i < rows.size(); ++i)
             rows[i] = &data[i*width_*output_components_];
 
         // read the data into the buffer
diff --git a/dlib/image_loader/jpeg_loader.h b/dlib/image_loader/jpeg_loader.h
index 3bf99c195..04c650dcc 100644
--- a/dlib/image_loader/jpeg_loader.h
+++ b/dlib/image_loader/jpeg_loader.h
@@ -43,10 +43,10 @@ namespace dlib
 #endif
             image_view<T> t(t_);
             t.set_size( height_, width_ );
-            for ( unsigned n = 0; n < height_;n++ )
+            for (size_t n = 0; n < height_;n++ )
             {
                 const unsigned char* v = get_row( n );
-                for ( unsigned m = 0; m < width_;m++ )
+                for (size_t m = 0; m < width_;m++ )
                 {
                     if ( is_gray() )
                     {
@@ -74,16 +74,16 @@ namespace dlib
         }
 
     private:
-        const unsigned char* get_row( unsigned long i ) const
+        const unsigned char* get_row(size_t i) const
         {
             return &data[i*width_*output_components_];
         }
         
         FILE * check_file(const char* filename );
         void read_image( FILE *file, const unsigned char* imgbuffer, size_t imgbuffersize );
-        unsigned long height_; 
-        unsigned long width_;
-        unsigned long output_components_;
+        size_t long height_; 
+        size_t long width_;
+        size_t long output_components_;
         std::vector<unsigned char> data;
     };