diff --git a/nix/devtools.nix b/nix/devtools.nix
index cf5ea8094..2dc43e22b 100644
--- a/nix/devtools.nix
+++ b/nix/devtools.nix
@@ -105,17 +105,16 @@ let
         name = "postgrest-dump-minimal-imports";
         docs = "Dump minimal imports into given directory.";
         inRootDir = true;
+        withTmpDir = true;
       }
       ''
         dumpdir="''${1:?dumpdir not set}"
-        tmpdir="$(mktemp -d)"
         mkdir -p "$dumpdir"
         ${cabal-install}/bin/cabal v2-build ${devCabalOptions} \
           --builddir="$tmpdir" \
           --ghc-option=-ddump-minimal-imports \
           --ghc-option=-dumpdir="$dumpdir" \
           1>&2
-        rm -rf "$tmpdir"
 
         # Fix OverloadedRecordFields imports
         # shellcheck disable=SC2016
@@ -127,12 +126,11 @@ let
       {
         name = "postgrest-hsie-minimal-imports";
         docs = "Run hsie with a provided dump of minimal imports.";
+        withTmpDir = true;
       }
       ''
-        tmpdir="$(mktemp -d)"
         ${dumpMinimalImports} "$tmpdir"
         ${hsie} "$tmpdir" "$@"
-        rm -rf "$tmpdir"
       '';
 
   hsieGraphModules =
diff --git a/nix/overlays/checked-shell-script/checked-shell-script.nix b/nix/overlays/checked-shell-script/checked-shell-script.nix
index 4e21d26db..a7fa8c95d 100644
--- a/nix/overlays/checked-shell-script/checked-shell-script.nix
+++ b/nix/overlays/checked-shell-script/checked-shell-script.nix
@@ -9,7 +9,7 @@
 , stdenv
 , writeTextFile
 }:
-{ name, docs, inRootDir ? false }: text:
+{ name, docs, inRootDir ? false, withTmpDir ? false }: text:
 # TODO: do something sensible with docs, e.g. provide automated --help
 let
   bin =
@@ -40,7 +40,19 @@ let
             exit 1
           fi
         ''
-        + "(${text})";
+        + lib.optionalString withTmpDir ''
+          tmpdir="$(mktemp -d)"
+
+          # we keep the tmpdir when an error occurs for debugging
+          trap 'echo Temporary directory kept at: $tmpdir' ERR
+          # remove the tmpdir when cancelled (postgrest-watch)
+          trap 'rm -rf "$tmpdir"' SIGINT SIGTERM
+        ''
+        + "(${text})"
+        + lib.optionalString withTmpDir ''
+
+          rm -rf "$tmpdir"
+        '';
 
       checkPhase =
         ''
diff --git a/nix/tests.nix b/nix/tests.nix
index 050712290..2334bc069 100644
--- a/nix/tests.nix
+++ b/nix/tests.nix
@@ -174,6 +174,7 @@ let
         inherit name;
         docs = "Run spec and io tests while collecting hpc coverage data.";
         inRootDir = true;
+        withTmpDir = true;
       }
       ''
         env="$(cat ${postgrest.env})"
@@ -184,14 +185,6 @@ let
         mkdir -p coverage
         rm -rf coverage/*
 
-        # temporary directory to collect data in
-        tmpdir="$(mktemp -d)"
-
-        # we keep the tmpdir when an error occurs for debugging
-        trap 'echo Temporary directory kept at: $tmpdir' ERR
-        # remove the tmpdir when cancelled (postgrest-watch)
-        trap 'rm -rf "$tmpdir"' SIGINT SIGTERM
-
         # build once before running all the tests
         ${cabal-install}/bin/cabal v2-build ${devCabalOptions} --enable-tests all
 
@@ -234,8 +227,6 @@ let
           echo "file://$(pwd)/coverage/hpc_index.html"
           ${ghc}/bin/hpc report coverage/postgrest.tix "$@"
         fi
-
-        rm -rf "$tmpdir"
       '';
 
   coverageDraftOverlay =