diff --git a/pkgs/overlays/unstable-from-source.nix b/pkgs/overlays/unstable-from-source.nix
deleted file mode 100644
index afb8f2e..0000000
--- a/pkgs/overlays/unstable-from-source.nix
+++ /dev/null
@@ -1,34 +0,0 @@
-{
-  unstableSource,
-}:
-
-self: super:
-
-let
-  useUnstable = self.config.useUnstable or true;
-  sanitizePlatform = platformConfig: self.lib.removeAttrs platformConfig [
-    "emulator"
-    "emulatorAvailable"
-  ];
-
-  unstablePkgsForNixpkgs = nixpkgs: import unstableSource {
-    # localSystem -> pkgs.stdenv.buildPlatform
-    localSystem = sanitizePlatform nixpkgs.stdenv.buildPlatform;
-    # crossSystem -> pkgs.stdenv.hostPlatform or pkgs.stdenv.targetPlatform ??
-    # passing below
-    # config -> pkgs.config
-    config = nixpkgs.config;
-    # overlays -> partial of pkgs.overlays
-    overlays = nixpkgs.overlays;
-    # crossOverlays -> partial of pkgs.overlays
-    # crossOverlays are merged to overlays, not sure what issues that might raise.
-    # ignoring.
-  } // (if nixpkgs.stdenv.buildPlatform == nixpkgs.stdenv.hostPlatform then {} else {
-    # workaround for some odd structured packages that changes behaviour
-    # when crossSystem is passed.
-    crossSystem = sanitizePlatform nixpkgs.stdenv.hostPlatform;
-  });
-in
-{
-  unstable = if useUnstable then unstablePkgsForNixpkgs self else self;
-}
diff --git a/pkgs/overlays/unstable.nix b/pkgs/overlays/unstable.nix
index 73e79b9..1cf4bae 100644
--- a/pkgs/overlays/unstable.nix
+++ b/pkgs/overlays/unstable.nix
@@ -2,9 +2,18 @@ self: super:
 
 let
   nixos = self.config.nixos or true;
+  unstableRevision = self.config.unstableRevision or null;
+  unstableRevisionHash = self.config.unstableRevisionHash or null;
   useUnstable = self.config.useUnstable or true;
 
-  unstablePkgsExprs = if nixos
+  unstablePkgsExprs = if !builtins.isNull unstableRevision
+    then if !builtins.isNull unstableRevisionHash
+      then builtins.fetchTarball {
+        url = "https://github.com/NixOS/nixpkgs/archive/${unstableRevision}.tar.gz";
+        sha256 = unstableRevisionHash;
+      }
+      else builtins.fetchTarball "https://github.com/NixOS/nixpkgs/archive/${unstableRevision}.tar.gz"
+    else if nixos
       then builtins.fetchTarball "https://channels.nixos.org/nixos-unstable/nixexprs.tar.xz"
       else builtins.fetchTarball "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";
 
@@ -15,10 +24,26 @@ let
   ];
 
   nixpkgsRevision = (builtins.readFile "${unstablePkgsExprs}/.git-revision");
+  unstablePkgsForNixpkgs = nixpkgs: import unstablePkgsExprs {
+    # localSystem -> pkgs.stdenv.buildPlatform
+    localSystem = nixpkgs.stdenv.buildPlatform;
+    # crossSystem -> pkgs.stdenv.hostPlatform or pkgs.stdenv.targetPlatform ??
+    # passing below
+    # config -> pkgs.config
+    config = nixpkgs.config;
+    # overlays -> partial of pkgs.overlays
+    overlays = nixpkgs.overlays;
+    # crossOverlays -> partial of pkgs.overlays
+    # crossOverlays are merged to overlays, not sure what issues that might raise.
+    # ignoring.
+  } // (if nixpkgs.stdenv.buildPlatform == nixpkgs.stdenv.hostPlatform then {} else {
+    # workaround for some odd structured packages that changes behaviour
+    # when crossSystem is passed.
+    crossSystem = nixpkgs.stdenv.hostPlatform;
+  });
 in
-import ./unstable-from-source.nix {
-  unstableSource = unstablePkgsExprs;
-} self super // {
+{
+  unstable = if useUnstable then unstablePkgsForNixpkgs self else self;
   unstableVersion = self.lib.optionalString useUnstable nixpkgsVersion;
   unstableRevision = self.lib.optionalString useUnstable nixpkgsRevision;
 }