diff --git a/pkgs/servers/identd/oidentd/default.nix b/pkgs/servers/identd/oidentd/default.nix
index 04ad25b3fd39..b8eb21e492bc 100644
--- a/pkgs/servers/identd/oidentd/default.nix
+++ b/pkgs/servers/identd/oidentd/default.nix
@@ -3,6 +3,8 @@
 stdenv.mkDerivation rec {
   name = "oidentd-2.0.8";
 
+  CFLAGS = [ "--std=gnu89" ];
+
   src = fetchurl {
     url = "mirror://sourceforge/ojnk/${name}.tar.gz";
     sha256 = "0vzv2086rrxcaavrm3js7aqvyc0grgaqy78x61d8s7r8hz8vwk55";