diff --git a/flake.nix b/flake.nix
index 1f9d5f64d..03106015b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -38,7 +38,6 @@
             # want to have an arbitrary order, since it might matter. being
             # explicit is better.
             (import ./nix/overlays/cargo-pgrx.nix)
-            (import ./nix/overlays/gdal-small.nix)
             (import ./nix/overlays/psql_16-oriole.nix)
 
           ];
@@ -68,15 +67,10 @@
               };
             })
             (import ./nix/overlays/cargo-pgrx-0-11-3.nix)
-            # (import ./nix/overlays/postgis.nix)
-            #(import ./nix/overlays/gdal-small.nix)
-
           ];
         };
         postgresql_15 = pkgs.postgresql.postgresql_15;
-        postgresql = pkgs.postgresql.postgresql_15;
         sfcgal = pkgs.callPackage ./nix/ext/sfcgal/sfcgal.nix { };
-        pg_regress = pkgs.callPackage ./nix/ext/pg_regress.nix { inherit postgresql; };
         supabase-groonga = pkgs.callPackage ./nix/supabase-groonga.nix { };
         mecab-naist-jdic = pkgs.callPackage ./nix/ext/mecab-naist-jdic/default.nix { };
         # Our list of PostgreSQL extensions which come from upstream Nixpkgs.
@@ -284,14 +278,41 @@
         # be used with 'nix build'. Don't use the names listed below; check the
         # name in 'nix flake show' in order to make sure exactly what name you
         # want.
-        basePackages = {
+        basePackages = let
+          # Function to get the PostgreSQL version from the attribute name
+          getVersion = name: 
+            let
+              match = builtins.match "psql_([0-9]+)" name;
+            in
+            if match == null then null else builtins.head match;
+
+          # Define the available PostgreSQL versions
+          postgresVersions = {
+            psql_15 = makePostgres "15";
+            # Uncomment the line below to enable PostgreSQL 16
+            # psql_16 = makePostgres "16";
+            # psql_orioledb_16 = makeOrioleDbPostgres "16_23" postgresql_orioledb_16;
+          };
+
+          # Find the active PostgreSQL version
+          activeVersion = getVersion (builtins.head (builtins.attrNames postgresVersions));
+
+          # Function to create the pg_regress package
+          makePgRegress = version:
+            let
+              postgresqlPackage = pkgs."postgresql_${version}";
+            in
+              pkgs.callPackage ./nix/ext/pg_regress.nix { 
+                postgresql = postgresqlPackage;
+              };
+
+        in 
+        postgresVersions //{
           supabase-groonga = supabase-groonga;
           # PostgreSQL versions.
           psql_15 = makePostgres "15";
-          #psql_16 = makePostgres "16";
           #psql_orioledb_16 = makeOrioleDbPostgres "16_23" postgresql_orioledb_16;
           sfcgal = sfcgal;
-          pg_regress = pg_regress;
           pg_prove = pkgs.perlPackages.TAPParserSourceHandlerpgTAP;
           postgresql_15 = pkgs.postgresql_15;
 
@@ -319,6 +340,7 @@
           };
           mecab_naist_jdic = mecab-naist-jdic;
           supabase_groonga = supabase-groonga;
+          pg_regress = makePgRegress activeVersion;
           # Start a version of the server.
           start-server =
             let
@@ -455,6 +477,7 @@
             sqlTests = ./nix/tests/smoke;
             pg_prove = pkgs.perlPackages.TAPParserSourceHandlerpgTAP;
             supabase-groonga = pkgs.callPackage ./nix/supabase-groonga.nix { };
+            pg_regress = basePackages.pg_regress;
           in
           pkgs.runCommand "postgres-${pgpkg.version}-check-harness"
             {
diff --git a/nix/ext/gdal.nix b/nix/ext/gdal.nix
new file mode 100644
index 000000000..83924d9ff
--- /dev/null
+++ b/nix/ext/gdal.nix
@@ -0,0 +1,69 @@
+{ lib
+, stdenv
+, fetchFromGitHub
+, cmake
+, pkg-config
+, curl
+, expat
+, libgeotiff
+, geos
+, json_c
+, libxml2
+, postgresql
+, proj
+, sqlite
+, libtiff
+, zlib
+}:
+
+stdenv.mkDerivation rec  {
+  pname = "gdal";
+  version = "3.8.5";
+
+  src = fetchFromGitHub {
+    owner = "OSGeo";
+    repo = "gdal";
+    rev = "v${version}";
+    hash = "sha256-Z+mYlyOX9vJ772qwZMQfCbD/V7RL6+9JLHTzoZ55ot0=";
+  };
+
+  nativeBuildInputs = [
+    cmake
+    pkg-config
+  ];
+
+  buildInputs = [
+    curl
+    expat
+    libgeotiff
+    geos
+    json_c
+    libxml2
+    postgresql
+    proj
+    sqlite
+    libtiff
+    zlib
+  ];
+
+  cmakeFlags = [
+    "-DGDAL_USE_INTERNAL_LIBS=OFF"
+    "-DGEOTIFF_INCLUDE_DIR=${lib.getDev libgeotiff}/include"
+    "-DGEOTIFF_LIBRARY_RELEASE=${lib.getLib libgeotiff}/lib/libgeotiff${stdenv.hostPlatform.extensions.sharedLibrary}"
+    "-DBUILD_PYTHON_BINDINGS=OFF"
+  ] ++ lib.optionals (!stdenv.isDarwin) [
+    "-DCMAKE_SKIP_BUILD_RPATH=ON"
+  ] ++ lib.optionals stdenv.isDarwin [
+    "-DCMAKE_BUILD_WITH_INSTALL_NAME_DIR=ON"
+  ];
+
+  enableParallelBuilding = true;
+
+  meta = with lib; {
+    description = "Translator library for raster geospatial data formats (PostGIS-focused build)";
+    homepage = "https://www.gdal.org/";
+    license = licenses.mit;
+    maintainers = with maintainers; teams.geospatial.members ++ [ marcweber dotlambda ];
+    platforms = platforms.unix;
+  };
+}
diff --git a/nix/ext/postgis.nix b/nix/ext/postgis.nix
index fcf1a8a56..bb9a6162a 100644
--- a/nix/ext/postgis.nix
+++ b/nix/ext/postgis.nix
@@ -5,7 +5,6 @@
 , postgresql
 , geos
 , proj
-, gdalMinimal
 , json_c
 , pkg-config
 , file
@@ -17,8 +16,8 @@
 }:
 
 let
-  gdal = gdalMinimal;
   sfcgal = callPackage ./sfcgal/sfcgal.nix { };
+  gdal = callPackage ./gdal.nix { inherit postgresql; };
 in
 stdenv.mkDerivation rec {
   pname = "postgis";
diff --git a/nix/overlays/gdal-small.nix b/nix/overlays/gdal-small.nix
deleted file mode 100644
index 18be8a526..000000000
--- a/nix/overlays/gdal-small.nix
+++ /dev/null
@@ -1,14 +0,0 @@
-final: prev: {
-  # override the version of gdal used with postgis with the small version.
-  # significantly reduces overall closure size
-  gdal = prev.gdalMinimal.override {
-    /* other features can be enabled, reference:
-        https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/gdal/default.nix
-        */
-
-    # useHDF = true;
-    # useArrow = true;
-    # useLibHEIF = true;
-    # ...
-  };
-}