diff --git a/README.md b/README.md
index f3f5af5..42b2c99 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,7 @@ The RV32I, RV32M, RV64I and RV64M ISAs are currently implemented but only RV32IM
 
 In no particular order:
 
+- Allow configurable limit for no. of running processes in order to prevent thrashing
 - Combine individual instruction checks into single ISA check (currently, doing so takes forever even when depth is set to only `20`)
 
 ## License
diff --git a/shell.nix b/shell.nix
index 07dd003..cf7e2e1 100644
--- a/shell.nix
+++ b/shell.nix
@@ -2,9 +2,9 @@ let
   pkgs = import <nixpkgs> { };
   nmigen-latest = pkgs.python3Packages.nmigen.overrideAttrs(oa: {
     src = pkgs.fetchFromGitHub {
-      owner = "DonaldKellett";
+      owner = "m-labs";
       repo = "nmigen";
-      rev = "03726c7e3f307f27626bcc7dffe75abe17b2a390";
+      rev = "39602ae3fdd143f3aa130278fb185cf3ff98d6da";
       sha256 = "1b0rjbb6is6nzbcnxrwh5iv4k9xcac0ijq5kp47wdg9rhbnaa5w0";
     };
   });