diff --git a/pkgs/servers/sql/postgresql/default.nix b/pkgs/servers/sql/postgresql/default.nix
index 69d01bb718e..bbb5a5a1774 100644
--- a/pkgs/servers/sql/postgresql/default.nix
+++ b/pkgs/servers/sql/postgresql/default.nix
@@ -23,7 +23,7 @@ let
     makeFlags = [ "world" ];
 
     preConfigure = ''
-    export CFLAGS="$CFLAGS -I${libxml2.dev}/include/libxml2"
+    export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -I${libxml2.dev}/include/libxml2"
     '';
     configureFlags = [
       "--with-openssl"