diff --git a/pkgs/development/ada-modules/gnatcoll/core.nix b/pkgs/development/ada-modules/gnatcoll/core.nix
index 0180558e1b96..a121eec212eb 100644
--- a/pkgs/development/ada-modules/gnatcoll/core.nix
+++ b/pkgs/development/ada-modules/gnatcoll/core.nix
@@ -3,39 +3,80 @@
 , gnat
 , gprbuild
 , fetchFromGitHub
+, fetchpatch2
 , which
+, python3
+, rsync
+, enableGnatcollCore ? true
+  # TODO(@sternenseemann): figure out a way to split this up into three packages
+, enableGnatcollProjects ? true
+  # for tests
+, gnatcoll-core
 }:
 
+# gnatcoll-projects depends on gnatcoll-core
+assert enableGnatcollProjects -> enableGnatcollCore;
+
 stdenv.mkDerivation rec {
   pname = "gnatcoll-core";
-  version = "24.0.0";
+  version = "25.0.0";
 
   src = fetchFromGitHub {
     owner = "AdaCore";
     repo = "gnatcoll-core";
     rev = "v${version}";
-    sha256 = "1cks2w0inj9hvamsdxjriwxnx1igmx2khhr6kwxshsl30rs8nzvb";
+    sha256 = "1srnh7vhs46c2zy4hcy4pg0a0prghfzlpv7c82k0jan384yz1g6g";
   };
 
+  patches = [
+    # Fix compilation with GNAT 12 https://github.com/AdaCore/gnatcoll-core/issues/88
+    (fetchpatch2 {
+      name = "gnatcoll-core-gnat-12.patch";
+      url = "https://github.com/AdaCore/gnatcoll-core/commit/515db1c9f1eea8095f2d9ff9570159a78c981ec6.patch";
+      sha256 = "1ghnkhp5fncb7qcmf59kyqvy0sd0pzf1phnr2z7b4ljwlkbmcp36";
+    })
+  ];
+
+  postPatch = ''
+    patchShebangs */*.gpr.py
+  '';
+
   nativeBuildInputs = [
     gprbuild
     which
     gnat
+    python3
+    rsync
   ];
 
   # propagate since gprbuild needs to find
   # referenced GPR project definitions
-  propagatedBuildInputs = [
+  propagatedBuildInputs = lib.optionals enableGnatcollProjects [
     gprbuild # libgpr
   ];
 
+  strictDeps = true;
+
   makeFlags = [
     "prefix=${placeholder "out"}"
     "PROCESSORS=$(NIX_BUILD_CORES)"
     # confusingly, for gprbuild --target is autoconf --host
     "TARGET=${stdenv.hostPlatform.config}"
+    "GNATCOLL_MINIMAL_ONLY=${if !enableGnatcollCore then "yes" else "no"}"
+    "GNATCOLL_PROJECTS=${if enableGnatcollProjects then "yes" else "no"}"
   ];
 
+  passthru.tests = {
+    minimalOnly = gnatcoll-core.override {
+      enableGnatcollProjects = false;
+      enableGnatcollCore = false;
+    };
+    noProjects = gnatcoll-core.override {
+      enableGnatcollProjects = false;
+      enableGnatcollCore = true;
+    };
+  };
+
   meta = with lib; {
     homepage = "https://github.com/AdaCore/gnatcoll-core";
     description = "GNAT Components Collection - Core packages";