diff --git a/pkgs/by-name/xc/xcur2png/malloc.diff b/pkgs/by-name/xc/xcur2png/malloc.diff
index 88f4e8e17ba9..d069db6a5297 100644
--- a/pkgs/by-name/xc/xcur2png/malloc.diff
+++ b/pkgs/by-name/xc/xcur2png/malloc.diff
@@ -16,7 +16,7 @@
  #include <X11/Xcursor/Xcursor.h>
 
 +
-+void *malloc ();
++void *malloc (size_t __size);
 +
 +/* Allocate an N-byte block of memory from the heap.
 +   If N is zero, allocate a 1-byte block.  */