diff --git a/pkgs/development/tools/misc/hydra/default.nix b/pkgs/development/tools/misc/hydra/default.nix
index 40a480a0909..7bed3b5d202 100644
--- a/pkgs/development/tools/misc/hydra/default.nix
+++ b/pkgs/development/tools/misc/hydra/default.nix
@@ -2,12 +2,12 @@
 
 {
   hydra-unstable = callPackage ./common.nix {
-    version = "2021-03-29";
+    version = "2021-04-29";
     src = fetchFromGitHub {
       owner = "NixOS";
       repo = "hydra";
-      rev = "9bb04ed97af047968196bad1728f927f7a6d905f";
-      sha256 = "sha256-gN/zNI2hGDMnYUjeGnU7SAuXP4KCmNqG+AYOVfINaQE=";
+      rev = "6047b1dd04d44acff9343b6b971ab609b73099d5";
+      sha256 = "sha256-E7JOHhSd4gIzE6FvSZVMxZE9WagbBkrfZVoibkanaYE=";
     };
     nix = nixFlakes;
 
diff --git a/pkgs/tools/package-management/nix/default.nix b/pkgs/tools/package-management/nix/default.nix
index 7eda5ae6f35..ac61a64180d 100644
--- a/pkgs/tools/package-management/nix/default.nix
+++ b/pkgs/tools/package-management/nix/default.nix
@@ -215,13 +215,13 @@ in rec {
   nixUnstable = lib.lowPrio (callPackage common rec {
     pname = "nix";
     version = "2.4${suffix}";
-    suffix = "pre20210326_dd77f71";
+    suffix = "pre20210503_6d2553a";
 
     src = fetchFromGitHub {
       owner = "NixOS";
       repo = "nix";
-      rev = "dd77f71afe6733e9790dd001125c423cb648b7ce";
-      sha256 = "rVHzrsCtdiWjyLuHnDplG2mx+7dw5VyzZ9ReXxuCvHY=";
+      rev = "6d2553ae1496288554e871c530836428f405fd67";
+      sha256 = "sha256-YeSeyOKhBAXHlkzo4mwYr8QIjIP9AgdpJ7YdhqOO2CA=";
     };
 
     inherit storeDir stateDir confDir boehmgc;