diff --git a/pkgs/development/compilers/ocaml/4.01.0.nix b/pkgs/development/compilers/ocaml/4.01.0.nix
index 48966fc2866..0f68014fad6 100644
--- a/pkgs/development/compilers/ocaml/4.01.0.nix
+++ b/pkgs/development/compilers/ocaml/4.01.0.nix
@@ -1,7 +1,14 @@
-{ stdenv, fetchurl, ncurses, buildEnv, libX11, xproto }:
+let
+  safeX11 = stdenv: !(stdenv.isArm || stdenv.isMips);
+in
+
+{ stdenv, fetchurl, ncurses, buildEnv, libX11, xproto, useX11 ? safeX11 stdenv }:
+
+if useX11 && !(safeX11 stdenv)
+  then throw "x11 not available in ocaml with arm or mips arch"
+  else # let the indentation flow
 
 let
-   useX11 = !stdenv.isArm && !stdenv.isMips;
    useNativeCompilers = !stdenv.isMips;
    inherit (stdenv.lib) optionals optionalString;
 in
diff --git a/pkgs/development/ocaml-modules/pcre/default.nix b/pkgs/development/ocaml-modules/pcre/default.nix
index 6df221a9244..b6c2488b250 100644
--- a/pkgs/development/ocaml-modules/pcre/default.nix
+++ b/pkgs/development/ocaml-modules/pcre/default.nix
@@ -1,11 +1,11 @@
 {stdenv, fetchurl, pcre, ocaml, findlib}:
 
 stdenv.mkDerivation {
-  name = "ocaml-pcre-7.0.4";
+  name = "ocaml-pcre-7.1.1";
 
   src = fetchurl {
-    url = https://bitbucket.org/mmottl/pcre-ocaml/downloads/pcre-ocaml-7.0.4.tar.gz;
-    sha256 = "0h2qlza7jkzgrglw1k0fydpbil0dgpv526kxyyd1apdbyzhb0mpw";
+    url = https://github.com/mmottl/pcre-ocaml/releases/download/v7.1.1/pcre-ocaml-7.1.1.tar.gz;
+    sha256 = "0nj4gb6hjjjmz5gnl9cjrh4w82rw8cvbwnk0hxhfgfd25p9k50n3";
   };
 
   buildInputs = [ocaml findlib];