diff --git a/rust/hg-core/src/dirstate/dirs_multiset.rs b/rust/hg-core/src/dirstate/dirs_multiset.rs
--- a/rust/hg-core/src/dirstate/dirs_multiset.rs
+++ b/rust/hg-core/src/dirstate/dirs_multiset.rs
@@ -30,7 +30,7 @@
     pub fn from_dirstate(
         vec: &HashMap<HgPathBuf, DirstateEntry>,
         skip_state: Option<EntryState>,
-    ) -> Self {
+    ) -> Result<Self, DirstateMapError> {
         let mut multiset = DirsMultiset {
             inner: HashMap::new(),
         };
@@ -39,27 +39,27 @@
             // This `if` is optimized out of the loop
             if let Some(skip) = skip_state {
                 if skip != *state {
-                    multiset.add_path(filename);
+                    multiset.add_path(filename)?;
                 }
             } else {
-                multiset.add_path(filename);
+                multiset.add_path(filename)?;
             }
         }
 
-        multiset
+        Ok(multiset)
     }
 
     /// Initializes the multiset from a manifest.
-    pub fn from_manifest(vec: &Vec<HgPathBuf>) -> Self {
+    pub fn from_manifest(vec: &Vec<HgPathBuf>) -> Result<Self, DirstateMapError> {
         let mut multiset = DirsMultiset {
             inner: HashMap::new(),
         };
 
         for filename in vec {
-            multiset.add_path(filename);
+            multiset.add_path(filename)?;
         }
 
-        multiset
+        Ok(multiset)
     }
 
     /// Increases the count of deepest directory contained in the path.
diff --git a/rust/hg-core/src/dirstate/dirstate_map.rs b/rust/hg-core/src/dirstate/dirstate_map.rs
--- a/rust/hg-core/src/dirstate/dirstate_map.rs
+++ b/rust/hg-core/src/dirstate/dirstate_map.rs
@@ -126,7 +126,7 @@
         }
         if old_state == EntryState::Unknown {
             if let Some(ref mut all_dirs) = self.all_dirs {
-                all_dirs.add_path(filename);
+                all_dirs.add_path(filename)?;
             }
         }
 
@@ -227,30 +227,32 @@
     /// emulate a Python lazy property, but it is ugly and unidiomatic.
     /// TODO One day, rewriting this struct using the typestate might be a
     /// good idea.
-    pub fn set_all_dirs(&mut self) {
+    pub fn set_all_dirs(&mut self) -> Result<(), DirstateMapError> {
         if self.all_dirs.is_none() {
             self.all_dirs =
-                Some(DirsMultiset::from_dirstate(&self.state_map, None));
+                Some(DirsMultiset::from_dirstate(&self.state_map, None)?);
         }
+        Ok(())
     }
 
-    pub fn set_dirs(&mut self) {
+    pub fn set_dirs(&mut self) -> Result<(), DirstateMapError> {
         if self.dirs.is_none() {
             self.dirs = Some(DirsMultiset::from_dirstate(
                 &self.state_map,
                 Some(EntryState::Removed),
-            ));
+            )?);
         }
+        Ok(())
     }
 
-    pub fn has_tracked_dir(&mut self, directory: &HgPath) -> bool {
-        self.set_dirs();
-        self.dirs.as_ref().unwrap().contains(directory)
+    pub fn has_tracked_dir(&mut self, directory: &HgPath) -> Result<bool, DirstateMapError> {
+        self.set_dirs()?;
+        Ok(self.dirs.as_ref().unwrap().contains(directory))
     }
 
-    pub fn has_dir(&mut self, directory: &HgPath) -> bool {
-        self.set_all_dirs();
-        self.all_dirs.as_ref().unwrap().contains(directory)
+    pub fn has_dir(&mut self, directory: &HgPath) -> Result<bool, DirstateMapError> {
+        self.set_all_dirs()?;
+        Ok(self.all_dirs.as_ref().unwrap().contains(directory))
     }
 
     pub fn parents(
diff --git a/rust/hg-cpython/src/dirstate/dirs_multiset.rs b/rust/hg-cpython/src/dirstate/dirs_multiset.rs
--- a/rust/hg-cpython/src/dirstate/dirs_multiset.rs
+++ b/rust/hg-cpython/src/dirstate/dirs_multiset.rs
@@ -47,6 +47,9 @@
         let inner = if let Ok(map) = map.cast_as::<PyDict>(py) {
             let dirstate = extract_dirstate(py, &map)?;
             DirsMultiset::from_dirstate(&dirstate, skip_state)
+                .map_err(|e| {
+                    PyErr::new::<exc::ValueError, _>(py, e.to_string())
+                })?
         } else {
             let map: Result<Vec<HgPathBuf>, PyErr> = map
                 .iter(py)?
@@ -57,6 +60,9 @@
                 })
                 .collect();
             DirsMultiset::from_manifest(&map?)
+                .map_err(|e| {
+                    PyErr::new::<exc::ValueError, _>(py, e.to_string())
+                })?
         };
 
         Self::create_instance(
diff --git a/rust/hg-cpython/src/dirstate/dirstate_map.rs b/rust/hg-cpython/src/dirstate/dirstate_map.rs
--- a/rust/hg-cpython/src/dirstate/dirstate_map.rs
+++ b/rust/hg-cpython/src/dirstate/dirstate_map.rs
@@ -200,6 +200,9 @@
         let d = d.extract::<PyBytes>(py)?;
         Ok(self.inner_shared(py).borrow_mut()?
             .has_tracked_dir(HgPath::new(d.data(py)))
+            .map_err(|e| {
+                PyErr::new::<exc::ValueError, _>(py, e.to_string())
+            })?
             .to_py_object(py))
     }
 
@@ -207,6 +210,9 @@
         let d = d.extract::<PyBytes>(py)?;
         Ok(self.inner_shared(py).borrow_mut()?
             .has_dir(HgPath::new(d.data(py)))
+            .map_err(|e| {
+                PyErr::new::<exc::ValueError, _>(py, e.to_string())
+            })?
             .to_py_object(py))
     }
 
@@ -330,24 +336,35 @@
 
     def getdirs(&self) -> PyResult<Dirs> {
         // TODO don't copy, share the reference
-        self.inner_shared(py).borrow_mut()?.set_dirs();
+        self.inner_shared(py).borrow_mut()?.set_dirs()
+            .map_err(|e| {
+                PyErr::new::<exc::ValueError, _>(py, e.to_string())
+            })?;
         Dirs::from_inner(
             py,
             DirsMultiset::from_dirstate(
                 &self.inner_shared(py).borrow(),
                 Some(EntryState::Removed),
-            ),
+            )
+            .map_err(|e| {
+                PyErr::new::<exc::ValueError, _>(py, e.to_string())
+            })?,
         )
     }
     def getalldirs(&self) -> PyResult<Dirs> {
         // TODO don't copy, share the reference
-        self.inner_shared(py).borrow_mut()?.set_all_dirs();
+        self.inner_shared(py).borrow_mut()?.set_all_dirs()
+            .map_err(|e| {
+                PyErr::new::<exc::ValueError, _>(py, e.to_string())
+            })?;
         Dirs::from_inner(
             py,
             DirsMultiset::from_dirstate(
                 &self.inner_shared(py).borrow(),
                 None,
-            ),
+            ).map_err(|e| {
+                PyErr::new::<exc::ValueError, _>(py, e.to_string())
+            })?,
         )
     }