diff --git a/dfx.nix b/dfx.nix
index 56634d18c1..c629d51cad 100644
--- a/dfx.nix
+++ b/dfx.nix
@@ -11,8 +11,9 @@
 , assets ? import ./assets.nix { inherit pkgs; }
 }:
 let
+  pkgs_glibc_2_27 = pkgs.pkgs_glibc_2_27;
   lib = pkgs.lib;
-  workspace = pkgs.buildDfinityRustPackage {
+  workspace = pkgs_glibc_2_27.buildDfinityRustPackage {
     name = "dfinity-sdk-rust";
     srcDir = ./.;
     regexes = [
@@ -54,7 +55,7 @@ let
   # add a `standalone` target stripped of nix references
   addStandalone = ws:
     ws // {
-      standalone = pkgs.lib.standaloneRust
+      standalone = lib.standaloneRust
         {
           drv = ws.build;
           exename = "dfx";
@@ -62,7 +63,7 @@ let
         };
     };
 
-  cc = pkgs.stdenv.cc;
+  cc = pkgs_glibc_2_27.stdenv.cc;
 
   # fixup the shell for more convenient developer use
   fixShell = ws:
@@ -82,7 +83,7 @@ let
           inputsFrom = [ ws.shell ];
           shellHook = ''
             # Set CARGO_HOME to minimize interaction with any environment outside nix
-            export CARGO_HOME=${if pkgs.lib.isHydra then "." else toString ./.}/.cargo-home
+            export CARGO_HOME=${if lib.isHydra then "." else toString ./.}/.cargo-home
 
             if [ ! -d "$CARGO_HOME" ]; then
                 mkdir -p $CARGO_HOME
diff --git a/nix/default.nix b/nix/default.nix
index c7d2e98659..e4d9aabe37 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -27,17 +27,27 @@ let
     sha256 = "0a2rhxli7ss4wixppfwks0hy3zpazwm9l3y2v9krrnyiska3qfrw";
   };
 
-  pkgs = import (commonSrc + "/pkgs") {
+  pkgs = mkPkgs [];
+
+  mkPkgs = e: import (commonSrc + "/pkgs") {
     inherit system isMaster labels;
     extraSources = sources;
     repoRoot = ../.;
-    overlays = [
+    overlays = e ++ [
       (
         self: super:
           let
             nixFmt = self.lib.nixFmt {};
           in
             {
+              pkgs_glibc_2_27 = mkPkgs [
+                (
+                  self: super: {
+
+                    glibc = self.glibc_2_27;
+                  }
+                )
+              ];
               motoko = import self.sources.motoko { inherit (self) system; };
               dfinity = (import self.sources.dfinity { inherit (self) system; }).dfinity.rs;
               napalm = self.callPackage self.sources.napalm {
diff --git a/nix/sources.json b/nix/sources.json
index 4fd24d8cd9..bcded9bcde 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -26,9 +26,9 @@
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "common": {
-        "branch": "master",
+        "branch": "johnw/hans",
         "repo": "ssh://git@github.com/dfinity-lab/common",
-        "rev": "52f0e0cdb97e371d9ada61249bccc875b51fec24",
+        "rev": "d8f7963cfb19f0b7149e787b875d0967cd9ecc80",
         "type": "git"
     },
     "dfinity": {