diff --git a/stdpopsim/slim_engine.py b/stdpopsim/slim_engine.py
index 71a566d78..5086b00bc 100644
--- a/stdpopsim/slim_engine.py
+++ b/stdpopsim/slim_engine.py
@@ -40,6 +40,7 @@
 
 import os
 import sys
+import contextlib
 import copy
 import string
 import tempfile
@@ -1474,48 +1475,52 @@ def simulate(
         tempdir = tempfile.TemporaryDirectory(prefix="stdpopsim_")
         ts_filename = os.path.join(tempdir.name, f"{os.urandom(3).hex()}.trees")
 
-        if slim_script:
-            script_filename = "stdout"
-            script_file = sys.stdout
-        else:
-            script_filename = os.path.join(tempdir.name, f"{os.urandom(3).hex()}.slim")
-            script_file = open(script_filename, "w")
-
-        recap_epoch = slim_makescript(
-            script_file,
-            ts_filename,
-            demographic_model,
-            contig,
-            samples,
-            extended_events,
-            slim_scaling_factor,
-            slim_burn_in,
-            slim_rate_map,
-            logfile=logfile,
-            logfile_interval=logfile_interval,
-        )
-
-        script_file.flush()
+        @contextlib.contextmanager
+        def script_file_f():
+            if run_slim:
+                fname = os.path.join(tempdir.name, f"{os.urandom(3).hex()}.slim")
+                f = open(fname, "w")
+            else:
+                fname = "stdout"
+                f = sys.stdout
+            yield f, fname
+            # Don't close sys.stdout.
+            if run_slim:
+                f.close()
+
+        with script_file_f() as sf:
+            script_file, script_filename = sf
+            recap_epoch = slim_makescript(
+                script_file,
+                ts_filename,
+                demographic_model,
+                contig,
+                samples,
+                extended_events,
+                slim_scaling_factor,
+                slim_burn_in,
+                slim_rate_map,
+                logfile=logfile,
+                logfile_interval=logfile_interval,
+            )
 
-        # Don't close sys.stdout.
-        if not slim_script:
-            script_file.close()
+            script_file.flush()
 
-        if not run_slim:
-            return None
+            if not run_slim:
+                return None
 
-        self._run_slim(
-            script_filename,
-            slim_path=slim_path,
-            seed=seed,
-            dry_run=dry_run,
-            verbosity=verbosity,
-        )
+            self._run_slim(
+                script_filename,
+                slim_path=slim_path,
+                seed=seed,
+                dry_run=dry_run,
+                verbosity=verbosity,
+            )
 
-        if dry_run:
-            return None
+            if dry_run:
+                return None
 
-        ts = tskit.load(ts_filename)
+            ts = tskit.load(ts_filename)
 
         ts = _add_dfes_to_metadata(ts, contig)
         if _recap_and_rescale: