diff --git a/pkgs/development/compilers/sbcl/default.nix b/pkgs/development/compilers/sbcl/default.nix
index 73d3cc08df88..112349190c1f 100644
--- a/pkgs/development/compilers/sbcl/default.nix
+++ b/pkgs/development/compilers/sbcl/default.nix
@@ -7,7 +7,9 @@
   coreutils,
   fetchurl,
   ps,
+  sbclPackages, # for passthru.tests
   strace,
+  stumpwm, # for passthru.tests
   texinfo,
   which,
   writableTmpDirAsHomeHook,
@@ -30,8 +32,8 @@ let
     "2.4.10".sha256 = "sha256-zus5a2nSkT7uBIQcKva+ylw0LOFGTD/j5FPy3hDF4vg=";
     # By unofficial and very loose convention we keep the latest version of
     # SBCL, and the previous one in case someone quickly needs to roll back.
-    "2.6.4".sha256 = "sha256-O6U+ZUtg/rfE9QRmGZ1tUmDyZhxxG6ItS3cLZVQA1Xs=";
     "2.6.5".sha256 = "sha256-kex19kclLtbmrq6bGhP0fHxs/ZtoSI3Gnxpv6lrMtEA=";
+    "2.6.6".sha256 = "sha256-plp6MIEqr1SSXRGSubnoEPUnx5kRxgALdUgQWu99o0s=";
   };
   # Collection of pre-built SBCL binaries for platforms that need them for
   # bootstrapping. Ideally these are to be avoided.  If ECL (or any other
@@ -308,6 +310,11 @@ stdenv.mkDerivation (finalAttrs: {
 
   __darwinAllowLocalNetworking = true;
 
+  passthru.tests = {
+    inherit stumpwm;
+    inherit (sbclPackages) iolib;
+  };
+
   meta = {
     # Broken since 2025-09-05 https://hydra.nixos.org/job/nixpkgs/staging-next/sbcl.x86_64-darwin
     broken = stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isx86_64;
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 1b5a0eec5df5..cbc946105b7d 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -7107,14 +7107,6 @@ with pkgs;
     ];
   };
 
-  sbcl_2_6_4 = wrapLisp {
-    pkg = callPackage ../development/compilers/sbcl { version = "2.6.4"; };
-    faslExt = "fasl";
-    flags = [
-      "--dynamic-space-size"
-      "3000"
-    ];
-  };
   sbcl_2_6_5 = wrapLisp {
     pkg = callPackage ../development/compilers/sbcl { version = "2.6.5"; };
     faslExt = "fasl";
@@ -7123,7 +7115,15 @@ with pkgs;
       "3000"
     ];
   };
-  sbcl = sbcl_2_6_5;
+  sbcl_2_6_6 = wrapLisp {
+    pkg = callPackage ../development/compilers/sbcl { version = "2.6.6"; };
+    faslExt = "fasl";
+    flags = [
+      "--dynamic-space-size"
+      "3000"
+    ];
+  };
+  sbcl = sbcl_2_6_6;
 
   sbclPackages = recurseIntoAttrs sbcl.pkgs;