diff --git a/pkgs/tools/graphics/netpbm/default.nix b/pkgs/tools/graphics/netpbm/default.nix
index 9de7603c973..b67e71c0fdf 100644
--- a/pkgs/tools/graphics/netpbm/default.nix
+++ b/pkgs/tools/graphics/netpbm/default.nix
@@ -15,7 +15,7 @@ stdenv.mkDerivation {
 
   postPatch = /* CVE-2005-2471, from Arch */ ''
     substituteInPlace converter/other/pstopnm.c \
-      --replace '"-DSAFER"' '"-DPARANOIDSAFER"'
+      --replace '"-dSAFER"' '"-dPARANOIDSAFER"'
   '';
 
   buildInputs =