diff --git a/memsync/harvest.py b/memsync/harvest.py
index 975773d..493bb5a 100644
--- a/memsync/harvest.py
+++ b/memsync/harvest.py
@@ -26,8 +26,8 @@ def cwd_to_project_key(cwd: Path) -> str:
         # Drive letter colon becomes a dash; backslashes become dashes
         # e.g. C:\Users\Ian\foo → C--Users-Ian-foo
         raw = str(cwd.resolve())
-        return raw.replace(":", "-").replace("\\", "-")
-    return str(cwd.resolve()).replace("/", "-")
+        return raw.replace(":", "-").replace("\\", "-").replace(" ", "-")
+    return str(cwd.resolve()).replace("/", "-").replace(" ", "-")
 
 
 def find_project_dir(
diff --git a/tests/test_harvest.py b/tests/test_harvest.py
index 9a2aef2..e1d345d 100644
--- a/tests/test_harvest.py
+++ b/tests/test_harvest.py
@@ -60,6 +60,20 @@ def test_nested_path(self):
         p = Path("/Users/ian/Documents/GitHub/memsync")
         assert cwd_to_project_key(p) == "-Users-ian-Documents-GitHub-memsync"
 
+    def test_spaces_in_path_unix(self):
+        if platform.system() == "Windows":
+            pytest.skip("Unix path test")
+        p = Path("/Users/ian/Documents/Untitled Gods Book")
+        assert cwd_to_project_key(p) == "-Users-ian-Documents-Untitled-Gods-Book"
+
+    def test_spaces_in_path_windows(self, monkeypatch):
+        if platform.system() != "Windows":
+            pytest.skip("Windows path test")
+        p = Path(r"C:\Users\ianfe\OneDrive\Documents\Untitled Gods Book")
+        key = cwd_to_project_key(p)
+        assert "Untitled-Gods-Book" in key
+        assert " " not in key
+
 
 # ---------------------------------------------------------------------------
 # find_project_dir