diff --git a/modules/juce_graphics/image_formats/pnglib/pngrutil.c b/modules/juce_graphics/image_formats/pnglib/pngrutil.c
index 7671ec46d0..b998fe6efe 100644
--- a/modules/juce_graphics/image_formats/pnglib/pngrutil.c
+++ b/modules/juce_graphics/image_formats/pnglib/pngrutil.c
@@ -456,7 +456,7 @@ png_inflate(png_structrp png_ptr, png_uint_32 owner, int finish,
       do
       {
          uInt avail;
-         Byte local_buffer[PNG_INFLATE_BUF_SIZE];
+         unsigned char local_buffer[PNG_INFLATE_BUF_SIZE];
 
          /* zlib INPUT BUFFER */
          /* The setting of 'avail_in' used to be outside the loop; by setting it
@@ -1360,8 +1360,8 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
             if (png_inflate_claim(png_ptr, png_iCCP,
                png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN ? 15 : 0) == Z_OK)
             {
-               Byte profile_header[132];
-               Byte local_buffer[PNG_INFLATE_BUF_SIZE];
+               unsigned char profile_header[132];
+               unsigned char local_buffer[PNG_INFLATE_BUF_SIZE];
                png_alloc_size_t size = (sizeof profile_header);
 
                png_ptr->zstream.next_in = (Bytef*)keyword + (keyword_length+2);