diff --git a/src/zopflipng/lodepng/lodepng_util.cpp b/src/zopflipng/lodepng/lodepng_util.cpp
index 574138a1..f1c00089 100644
--- a/src/zopflipng/lodepng/lodepng_util.cpp
+++ b/src/zopflipng/lodepng/lodepng_util.cpp
@@ -1151,7 +1151,7 @@ unsigned convertToXYZ(float* out, float whitepoint[3], const unsigned char* in,
     use_icc = validateICC(&icc);
   }
 
-  data = (unsigned char*)lodepng_malloc(w * h * (bit16 ? 8 : 4));
+  data = (unsigned char*)lodepng_malloc((size_t)w * h * (bit16 ? 8 : 4));
   error = lodepng_convert(data, in, &tempmode, mode_in, w, h);
   if(error) goto cleanup;