diff --git a/core/results.py b/core/results.py
index 3606e38a..1ba728a9 100644
--- a/core/results.py
+++ b/core/results.py
@@ -10,6 +10,7 @@ import logging
 import re
 import os
 import os.path as op
+from errno import EISDIR, EACCES
 from xml.etree import ElementTree as ET
 
 from hscommon.jobprogress.job import nulljob
@@ -376,8 +377,8 @@ class Results(Markable):
             do_write(outfile)
         except OSError as e:
             # If our OSError is because dest is already a directory, we want to handle that. 21 is
-            # the code we get on OS X and Linux, 13 is what we get on Windows.
-            if e.errno in {21, 13}:
+            # the code we get on OS X and Linux (EISDIR), 13 is what we get on Windows (EACCES).
+            if e.errno in (EISDIR, EACCES):
                 p = str(outfile)
                 dirname, basename = op.split(p)
                 otherfiles = os.listdir(dirname)
diff --git a/hscommon/conflict.py b/hscommon/conflict.py
index af133ac7..0675efd0 100644
--- a/hscommon/conflict.py
+++ b/hscommon/conflict.py
@@ -14,6 +14,7 @@ import re
 import os
 import shutil
 
+from errno import EISDIR, EACCES
 from pathlib import Path
 from typing import Callable, List
 
@@ -75,10 +76,8 @@ def smart_copy(source_path: Path, dest_path: Path) -> None:
     try:
         _smart_move_or_copy(shutil.copy, source_path, dest_path)
     except OSError as e:
-        if e.errno in {
-            21,
-            13,
-        }:  # it's a directory, code is 21 on OS X / Linux and 13 on Windows
+        # It's a directory, code is 21 on OS X / Linux (EISDIR) and 13 on Windows (EACCES)
+        if e.errno in (EISDIR, EACCES):
             _smart_move_or_copy(shutil.copytree, source_path, dest_path)
         else:
             raise