diff --git a/builder/comp-builder.nix b/builder/comp-builder.nix
index 808d8c89dd..9cd2b9f90d 100644
--- a/builder/comp-builder.nix
+++ b/builder/comp-builder.nix
@@ -1,6 +1,4 @@
 { pkgs, stdenv, buildPackages, pkgsBuildBuild, ghc, llvmPackages, lib, gobject-introspection ? null, haskellLib, makeConfigFiles, haddockBuilder, ghcForComponent, hsPkgs, compiler, runCommand, libffi, gmp, windows, zlib, ncurses, nodejs, nonReinstallablePkgs }@defaults:
-lib.makeOverridable (
-let self =
 { componentId
 , component
 , package
@@ -92,7 +90,76 @@ let self =
 # LLVM
 , useLLVM ? ghc.useLLVM or false
 , smallAddressSpace ? false
-
+}:
+# makeOverridable is called here after all the `? DEFAULT` arguments
+# will have been applied.  This makes sure that `c.override (oldAttrs: {...})`
+# includes these `DEFAULT` values in `oldAttrs`.  This is important
+# so that overrides can modify the existing values instead of replacing them.
+lib.makeOverridable (
+let self =
+{ componentId
+, component
+, package
+, name
+, setup
+, src
+, flags
+, cabalFile
+, cabal-generator
+, patches
+, preUnpack
+, configureFlags
+, prePatch
+, postPatch
+, preConfigure
+, postConfigure
+, setupBuildFlags
+, preBuild
+, postBuild
+, preCheck
+, postCheck
+, setupInstallFlags
+, preInstall
+, postInstall
+, preHaddock
+, postHaddock
+, shellHook
+, configureAllComponents
+, allComponent
+, build-tools
+, pkgconfig
+, platforms
+, frameworks
+, dontPatchELF
+, dontStrip
+, dontUpdateAutotoolsGnuConfigScripts
+, hardeningDisable
+, enableStatic
+, enableShared
+, enableExecutableDynamic
+, enableDeadCodeElimination
+, writeHieFiles
+, ghcOptions
+, contentAddressed
+, doHaddock
+, doHoogle
+, hyperlinkSource
+, quickjump
+, keepConfigFiles
+, keepGhc
+, keepSource
+, setupHaddockFlags
+, enableLibraryProfiling
+, enableProfiling
+, profilingDetail
+, doCoverage
+, enableSeparateDataOutput
+, enableLibraryForGhci
+, enableDebugRTS
+, enableDWARF
+, enableTSanRTS
+, useLLVM
+, smallAddressSpace
 }@drvArgs:
 
 let
@@ -719,4 +786,68 @@ let
   // lib.optionalAttrs (hardeningDisable != [] || stdenv.hostPlatform.isMusl) {
     hardeningDisable = hardeningDisable ++ lib.optional stdenv.hostPlatform.isMusl "pie";
   });
-in drv; in self)
+in drv; in self) {
+  inherit componentId
+          component
+          package
+          name
+          setup
+          src
+          flags
+          cabalFile
+          cabal-generator
+          patches
+          preUnpack
+          configureFlags
+          prePatch
+          postPatch
+          preConfigure
+          postConfigure
+          setupBuildFlags
+          preBuild
+          postBuild
+          preCheck
+          postCheck
+          setupInstallFlags
+          preInstall
+          postInstall
+          preHaddock
+          postHaddock
+          shellHook
+          configureAllComponents
+          allComponent
+          build-tools
+          pkgconfig
+          platforms
+          frameworks
+          dontPatchELF
+          dontStrip
+          dontUpdateAutotoolsGnuConfigScripts
+          hardeningDisable
+          enableStatic
+          enableShared
+          enableExecutableDynamic
+          enableDeadCodeElimination
+          writeHieFiles
+          ghcOptions
+          contentAddressed
+          doHaddock
+          doHoogle
+          hyperlinkSource
+          quickjump
+          keepConfigFiles
+          keepGhc
+          keepSource
+          setupHaddockFlags
+          enableLibraryProfiling
+          enableProfiling
+          profilingDetail
+          doCoverage
+          enableSeparateDataOutput
+          enableLibraryForGhci
+          enableDebugRTS
+          enableDWARF
+          enableTSanRTS
+          useLLVM
+          smallAddressSpace;
+}
diff --git a/lib/check.nix b/lib/check.nix
index 5b9a643560..15270975e5 100644
--- a/lib/check.nix
+++ b/lib/check.nix
@@ -3,7 +3,7 @@ let self = drvOrig:
 
 let
   # Work around problem running dynamicially linked Android executables with qemu.
-  drv = drvOrig.override (lib.optionalAttrs stdenv.hostPlatform.isAndroid { setupBuildFlags = ["--ghc-option=-optl-static" ]; });
+  drv = drvOrig.override (oldAttrs: lib.optionalAttrs stdenv.hostPlatform.isAndroid { setupBuildFlags = (oldAttrs.setupBuildFlags or []) ++ ["--ghc-option=-optl-static"]; });
 
   component = drv.config;
 
diff --git a/test/th-dlls/default.nix b/test/th-dlls/default.nix
index a25fe93b74..8ec1425654 100644
--- a/test/th-dlls/default.nix
+++ b/test/th-dlls/default.nix
@@ -43,9 +43,9 @@ in recurseIntoAttrs {
   };
 
   build = packages.th-dlls.components.library;
-  just-template-haskell = packages.th-dlls.components.exes.just-template-haskell;
+  just-template-haskell = haskellLib.check packages.th-dlls.components.exes.just-template-haskell;
   build-ei = packages-ei.th-dlls.components.library;
-  just-template-haskell-ei = packages-ei.th-dlls.components.exes.just-template-haskell;
+  just-template-haskell-ei = haskellLib.check packages-ei.th-dlls.components.exes.just-template-haskell;
 } // optionalAttrs
     (!(builtins.elem compiler-nix-name ["ghc984" "ghc9122" "ghc9122llvm" "ghc91320250523"]  && stdenv.buildPlatform.isx86_64 && stdenv.hostPlatform.isAarch64
       # The dependency on `math-functions` somehow breaks GHC 9.6.7 musl profiled builds (only with the external interpreter though)