--- source/base/image/png.cpp
+++ source/base/image/png.cpp
@@ -433,7 +433,7 @@
       entry.alpha = 1.0f ;
       if (has_alpha)
         if (index < r_info_ptr->num_trans)
-          entry.alpha = (float) (r_info_ptr->trans[index]) / 255.0;
+          entry.alpha = (float) (r_info_ptr->trans_alpha[index]) / 255.0;
       colormap.push_back (entry);
     }
 
@@ -459,7 +459,7 @@
       entry.alpha = 1.0f ;
       if (r_info_ptr->valid & PNG_INFO_tRNS)
         if (index < r_info_ptr->num_trans)
-          entry.alpha = (float) (r_info_ptr->trans[index]) / 255.0;
+          entry.alpha = (float) (r_info_ptr->trans_alpha[index]) / 255.0;
       colormap.push_back (entry);
     }