diff --git a/src/dictionary/layered.rs b/src/dictionary/layered.rs
index 75e1c4c9..87d4465a 100644
--- a/src/dictionary/layered.rs
+++ b/src/dictionary/layered.rs
@@ -140,6 +140,13 @@ impl Dictionary for Layered {
         None
     }
 
+    fn is_readonly(&self) -> bool {
+        self.sys_dict
+            .iter()
+            .chain(iter::once(&self.user_dict))
+            .any(|d| !d.is_readonly())
+    }
+
     fn reopen(&mut self) -> Result<(), UpdateDictionaryError> {
         self.user_dict.reopen()
     }
@@ -347,6 +354,7 @@ mod tests {
             dict.remove_phrase(&[syl![Bopomofo::C, Bopomofo::E, Bopomofo::TONE4]], "冊")
                 .is_err()
         );
+        assert!(dict.is_readonly());
         Ok(())
     }
 }
diff --git a/src/dictionary/mod.rs b/src/dictionary/mod.rs
index c6486952..41bc07e9 100644
--- a/src/dictionary/mod.rs
+++ b/src/dictionary/mod.rs
@@ -347,6 +347,8 @@ pub trait Dictionary: Debug {
     fn about(&self) -> DictionaryInfo;
     /// Returns the dictionary file path if it's backed by a file.
     fn path(&self) -> Option<&Path>;
+    /// Returns whether the dictionary was opened readonly.
+    fn is_readonly(&self) -> bool;
     /// Reopens the dictionary if it was changed by a different process
     ///
     /// It should not fail if the dictionary is read-only or able to sync across
diff --git a/src/dictionary/sqlite.rs b/src/dictionary/sqlite.rs
index dcfa8729..392b8fda 100644
--- a/src/dictionary/sqlite.rs
+++ b/src/dictionary/sqlite.rs
@@ -382,6 +382,10 @@ impl Dictionary for SqliteDictionary {
         self.path.as_ref().map(|p| p as &Path)
     }
 
+    fn is_readonly(&self) -> bool {
+        self.readonly
+    }
+
     fn reopen(&mut self) -> Result<(), UpdateDictionaryError> {
         Ok(())
     }
diff --git a/src/dictionary/trie.rs b/src/dictionary/trie.rs
index f0ea822a..dda87488 100644
--- a/src/dictionary/trie.rs
+++ b/src/dictionary/trie.rs
@@ -419,6 +419,10 @@ impl Dictionary for Trie {
     fn path(&self) -> Option<&Path> {
         self.path.as_ref().map(|p| p as &Path)
     }
+
+    fn is_readonly(&self) -> bool {
+        true
+    }
 }
 
 fn context_specific<T: EncodeValue + Tagged>(
diff --git a/src/dictionary/trie_buf.rs b/src/dictionary/trie_buf.rs
index 933e0bae..d32bccc3 100644
--- a/src/dictionary/trie_buf.rs
+++ b/src/dictionary/trie_buf.rs
@@ -23,6 +23,7 @@ pub struct TrieBuf {
     graveyard: BTreeSet<PhraseKey>,
     join_handle: Option<JoinHandle<Result<(), UpdateDictionaryError>>>,
     dirty: bool,
+    readonly: bool,
 }
 
 type PhraseKey = (Cow<'static, [Syllable]>, Cow<'static, str>);
@@ -61,6 +62,7 @@ impl TrieBuf {
             graveyard: BTreeSet::new(),
             join_handle: None,
             dirty: false,
+            readonly: false,
         })
     }
 
@@ -72,6 +74,7 @@ impl TrieBuf {
             graveyard: BTreeSet::new(),
             join_handle: None,
             dirty: false,
+            readonly: false,
         }
     }
 
@@ -257,6 +260,7 @@ impl TrieBuf {
             graveyard: self.graveyard.clone(),
             join_handle: None,
             dirty: false,
+            readonly: false,
         };
         self.join_handle = Some(thread::spawn(move || {
             let mut builder = TrieBuilder::new();
@@ -304,6 +308,10 @@ impl Dictionary for TrieBuf {
         self.trie.as_ref()?.path()
     }
 
+    fn is_readonly(&self) -> bool {
+        self.readonly
+    }
+
     fn reopen(&mut self) -> Result<(), UpdateDictionaryError> {
         self.sync()?;
         Ok(())