diff --git a/src/app/doc.cpp b/src/app/doc.cpp
index d4e636e34..95627d8b8 100644
--- a/src/app/doc.cpp
+++ b/src/app/doc.cpp
@@ -515,12 +515,9 @@ Doc* Doc::duplicate(DuplicateType type) const
   // Copy slices
   for (const Slice *slice : sourceSprite->slices()) {
     auto sliceCopy = new Slice(*slice);
-    sliceCopy->setUserData(slice->userData());
-
-    for (frame_t i(0); i < sourceSprite->totalFrames(); ++i)
-      sliceCopy->insert(i, *slice->getByFrame(i));
-
     spriteCopy->slices().add(sliceCopy);
+
+    ASSERT(sliceCopy->owner() == &spriteCopy->slices());
   }
 
   // Copy color palettes
diff --git a/src/doc/keyframes.h b/src/doc/keyframes.h
index e6c80a896..cb0c980db 100644
--- a/src/doc/keyframes.h
+++ b/src/doc/keyframes.h
@@ -8,7 +8,6 @@
 #define DOC_KEYFRAMES_H_INCLUDED
 #pragma once
 
-#include "base/disable_copying.h"
 #include "doc/frame.h"
 
 #include <vector>
@@ -111,6 +110,11 @@ namespace doc {
 
     Keyframes() { }
 
+    Keyframes(const Keyframes& other) {
+      for (const auto& key : other.m_keys)
+        m_keys.push_back(Key(key.frame(), new T(*key.value())));
+    }
+
     void insert(const frame_t frame, T* value) {
       auto it = getIterator(frame);
       if (it == end())
@@ -189,9 +193,6 @@ namespace doc {
 
   private:
     List m_keys;
-
-    // Disable operator=
-    DISABLE_COPYING(Keyframes);
   };
 
 } // namespace doc
diff --git a/src/doc/slice.cpp b/src/doc/slice.cpp
index b7f5904ff..e50275e5e 100644
--- a/src/doc/slice.cpp
+++ b/src/doc/slice.cpp
@@ -42,13 +42,13 @@ Slice::Slice()
 }
 
 Slice::Slice(const Slice& other)
-  : WithUserData(ObjectType::Slice)
+  : WithUserData(other)
   , m_owner(nullptr)
   , m_name(other.m_name)
+  , m_keys(other.m_keys)
 {
 }
 
-
 Slice::~Slice()
 {
   ASSERT(!m_owner);