diff --git a/pkgs/development/compilers/llvm/15/llvm/default.nix b/pkgs/development/compilers/llvm/15/llvm/default.nix
index 40fb105cdc523..e0b79a9acfefc 100644
--- a/pkgs/development/compilers/llvm/15/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/15/llvm/default.nix
@@ -255,6 +255,38 @@ in stdenv.mkDerivation (rec {
     )
   '';
 
+  # Defensive check: some paths (that we make symlinks to) depend on the release
+  # version, for example:
+  #  - https://github.com/llvm/llvm-project/blob/406bde9a15136254f2b10d9ef3a42033b3cb1b16/clang/lib/Headers/CMakeLists.txt#L185
+  #
+  # So we want to sure that the version in the source matches the release
+  # version we were given.
+  #
+  # We do this check here, in the LLVM build, because it happens early.
+  postConfigure = let
+    v = lib.versions;
+    major = v.major release_version;
+    minor = v.minor release_version;
+    patch = v.patch release_version;
+  in ''
+    # $1: part, $2: expected
+    check_version() {
+      part="''${1^^}"
+      part="$(cat include/llvm/Config/llvm-config.h  | grep "#define LLVM_VERSION_''${part} " | cut -d' ' -f3)"
+
+      if [[ "$part" != "$2" ]]; then
+        echo >&2 \
+          "mismatch in the $1 version! we have version ${release_version}" \
+          "and expected the $1 version to be '$2'; the source has '$part' instead"
+        exit 3
+      fi
+    }
+
+    check_version major ${major}
+    check_version minor ${minor}
+    check_version patch ${patch}
+  '';
+
   # E.g. mesa.drivers use the build-id as a cache key (see #93946):
   LDFLAGS = optionalString (enableSharedLibraries && !stdenv.isDarwin) "-Wl,--build-id=sha1";