diff --git a/src/meshlabplugins/filter_photosynth/downloader.cpp b/src/meshlabplugins/filter_photosynth/downloader.cpp
index e60d0e3fb..c26e071f5 100644
--- a/src/meshlabplugins/filter_photosynth/downloader.cpp
+++ b/src/meshlabplugins/filter_photosynth/downloader.cpp
@@ -683,7 +683,7 @@ float readBigEndianSingle(QIODevice *device, bool &error)
     if(error)
       return -1;
   }
-  char reversed[] = { bytes[3],bytes[2],bytes[1],bytes[0] };
+  unsigned char reversed[] = { bytes[3],bytes[2],bytes[1],bytes[0] };
 
   float *f = (float *)(&  reversed[0]);
   return*f;