diff --git a/default.nix b/default.nix
index 15b4ff6a..3dc4c983 100644
--- a/default.nix
+++ b/default.nix
@@ -1,7 +1,7 @@
-{ nixpkgs ? import ./nixpkgs.nix, enableOpencv4 ? false
+{ nixpkgs ? import ./nixpkgs.nix
 , system ? builtins.currentSystem
 }:
 import nixpkgs {
   inherit system;
-  overlays = [ (import ./overlay.nix enableOpencv4) ];
+  overlays = [ (import ./overlay.nix) ];
 }
diff --git a/nix/sources.json b/nix/sources.json
index 957823ba..04314a22 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -12,15 +12,15 @@
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs": {
-        "branch": "nixos-unstable",
-        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
+        "branch": "nixos-23.05",
+        "description": " Nix Packages collection & NixOS",
         "homepage": "https://github.com/NixOS/nixpkgs",
         "owner": "NixOS",
-        "repo": "nixpkgs-channels",
-        "rev": "8d1510abfb592339e13ce8f6db6f29c1f8b72924",
-        "sha256": "0i4jscq2qy2vn9kr8ix9gr8ncf9dss24y09jrqhlpcpryi4i98dc",
+        "repo": "nixpkgs",
+        "rev": "da5adce0ffaff10f6d0fee72a02a5ed9d01b52fc",
+        "sha256": "sha256-32EnPCaVjOiEERZ+o/2Ir7JH9pkfwJZJ27SKHNvt4yk=",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs-channels/archive/8d1510abfb592339e13ce8f6db6f29c1f8b72924.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/da5adce0ffaff10f6d0fee72a02a5ed9d01b52fc.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }
diff --git a/overlay.nix b/overlay.nix
index cf25d793..3fbab8b3 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -1,12 +1,8 @@
-enableOpencv4 : final : previous : with final.lib; with final.haskell.lib;
+final : previous : with final.lib; with final.haskell.lib;
 let
-  handleOpencv4 = drv : if enableOpencv4 then enableCabalFlag drv "opencv4" else drv;
-
   useOpencvHighgui = drv : overrideCabal drv (_drv: {
     libraryPkgconfigDepends = [
-      (if enableOpencv4
-       then final.opencv4_highgui
-       else final.opencv3_highgui)
+      final.opencv4_highgui
     ];
   });
 
@@ -19,7 +15,7 @@ let
         ]);
       });
     in {
-      opencv = handleOpencv4 (addBuildToolsInShell (doBenchmark (overrideCabal (super.callCabal2nix "opencv" ./opencv {}) (drv : {
+      opencv = addBuildToolsInShell (doBenchmark (overrideCabal (super.callCabal2nix "opencv" ./opencv {}) (drv : {
         src = final.runCommand "opencv-src"
           { files = final.lib.sourceByRegex ./opencv [
               "^src$"
@@ -46,9 +42,8 @@ let
         shellHook = ''
           export hardeningDisable=bindnow
         '';
-      } // optionalAttrs enableOpencv4 {
         libraryPkgconfigDepends = [ final.opencv4 ];
-      }))));
+      })));
 
       opencv_highgui = useOpencvHighgui self.opencv;
 
@@ -73,7 +68,7 @@ let
         }))).override { opencv = self.opencv_highgui; };
 
       opencv-extra =
-        handleOpencv4 (addBuildToolsInShell (overrideCabal (super.callCabal2nix "opencv-extra" ./opencv-extra {}) (_drv : {
+        addBuildToolsInShell (overrideCabal (super.callCabal2nix "opencv-extra" ./opencv-extra {}) (_drv : {
           src = final.runCommand "opencv-extra-src"
             { files = final.lib.sourceByRegex ./opencv-extra [
                 "^include$"
@@ -98,11 +93,9 @@ let
           '';
           # TODO (BvD): This should be added by cabal2nix. Fix this upstream.
           libraryPkgconfigDepends = [
-            (if enableOpencv4
-             then final.opencv4
-             else final.opencv3)
+            final.opencv4
           ];
-        })));
+        }));
 
       opencv-extra_highgui = (useOpencvHighgui self.opencv-extra).override {
         opencv = self.opencv_highgui;
@@ -137,9 +130,6 @@ in  {
       haskellOverrides self super;
   };
 
-  opencv3_highgui = previous.opencv3.override {
-    enableGtk3 = !final.stdenv.isDarwin;
-  };
   opencv4_highgui = previous.opencv4.override {
     enableGtk3 = !final.stdenv.isDarwin;
   };
diff --git a/stack.yaml b/stack.yaml
index afd6e1d3..1147973f 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,5 @@
-resolver: lts-20.26
+resolver: lts-20.26 # ghc-9.2.8
+# resolver: lts-20.11 # ghc-9.2.5
 packages:
 - opencv/
 - opencv-examples/
@@ -12,12 +13,14 @@ packages:
 
 allow-newer: true
 
-extra-lib-dirs:
-- /usr/local/lib
-
 nix:
-  path: [ "nixpkgs=https://github.com/NixOS/nixpkgs/archive/8d1510abfb592339e13ce8f6db6f29c1f8b72924.tar.gz" ]
-  packages: [ zlib pkgconfig opencv3 ]
+  path: [ "nixpkgs=https://github.com/NixOS/nixpkgs/archive/da5adce0ffaff10f6d0fee72a02a5ed9d01b52fc.tar.gz" ] # nixos-22.11 with opencv4-4.7, and providing ghc-9.2.8
+  # path: [ "nixpkgs=https://github.com/NixOS/nixpkgs/archive/ea4c80b39be4c09702b0cb3b42eab59e2ba4f24b.tar.gz" ] # nixos-22.11 with opencv4-4.6, and providing ghc-9.2.5
+  packages:
+  - zlib
+  - gmp
+  - pkg-config
+  - opencv4
 
 # Uncomment if you wish to use Docker integration
 # See README.md for further information.