diff --git a/src/index_map.rs b/src/index_map.rs
index 50d021f..b96179f 100644
--- a/src/index_map.rs
+++ b/src/index_map.rs
@@ -238,9 +238,13 @@ impl<K: Eq + Hash, V, S: Default> Default for FrozenIndexMap<K, V, S> {
 
 impl<K: Clone, V: Clone, S: Clone> Clone for FrozenIndexMap<K, V, S> {
     fn clone(&self) -> Self {
-        Self {
+        assert!(!self.in_use.get());
+        self.in_use.set(true);
+        let self_clone = Self {
             map: unsafe { self.map.get().as_ref().unwrap() }.clone().into(),
-            in_use: self.in_use.clone(),
-        }
+            in_use: Cell::from(false),
+        };
+        self.in_use.set(false);
+        return self_clone;
     }
 }
diff --git a/src/index_set.rs b/src/index_set.rs
index 28819d0..59588ad 100644
--- a/src/index_set.rs
+++ b/src/index_set.rs
@@ -183,9 +183,13 @@ impl<T: Eq + Hash, S: Default> Default for FrozenIndexSet<T, S> {
 
 impl<K: Clone, V: Clone> Clone for FrozenIndexSet<K, V> {
     fn clone(&self) -> Self {
-        Self {
+        assert!(!self.in_use.get());
+        self.in_use.set(true);
+        let self_clone = Self {
             set: unsafe { self.set.get().as_ref().unwrap() }.clone().into(),
-            in_use: self.in_use.clone(),
-        }
+            in_use: Cell::from(false),
+        };
+        self.in_use.set(false);
+        return self_clone;
     }
 }
diff --git a/src/map.rs b/src/map.rs
index e8cf7c1..32e79a8 100644
--- a/src/map.rs
+++ b/src/map.rs
@@ -272,11 +272,14 @@ impl<K: Eq + Hash, V, S: Default> Default for FrozenMap<K, V, S> {
 
 impl<K: Clone, V: Clone, S: Clone> Clone for FrozenMap<K, V, S> {
     fn clone(&self) -> Self {
-        Self {
+        assert!(!self.in_use.get());
+        self.in_use.set(true);
+        let self_clone = Self {
             map: unsafe { self.map.get().as_ref().unwrap() }.clone().into(),
-            in_use: self.in_use.clone(),
-        }
-    }
+            in_use: Cell::from(false),
+        };
+        self.in_use.set(false);
+        return self_clone;}
 }
 
 /// Append-only version of `std::collections::BTreeMap` where
@@ -507,9 +510,12 @@ impl<K: Clone + Ord, V: StableDeref> Default for FrozenBTreeMap<K, V> {
 
 impl<K: Clone, V: Clone> Clone for FrozenBTreeMap<K, V> {
     fn clone(&self) -> Self {
-        Self {
+        assert!(!self.in_use.get());
+        self.in_use.set(true);
+        let self_clone = Self {
             map: unsafe { self.map.get().as_ref().unwrap() }.clone().into(),
-            in_use: self.in_use.clone(),
-        }
-    }
+            in_use: Cell::from(false),
+        };
+        self.in_use.set(false);
+        return self_clone;}
 }