diff --git a/pngset.c b/pngset.c
index 6f3a1ee11..795a17633 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1017,7 +1017,7 @@ png_set_tRNS(png_structrp png_ptr, png_inforp info_ptr,
        {
          /* Changed from num_trans to PNG_MAX_PALETTE_LENGTH in version 1.2.1 */
           info_ptr->trans_alpha = png_voidcast(png_bytep,
-              png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH));
+              png_calloc(png_ptr, PNG_MAX_PALETTE_LENGTH));
           memcpy(info_ptr->trans_alpha, trans_alpha, (png_size_t)num_trans);
        }
        png_ptr->trans_alpha = info_ptr->trans_alpha;