diff --git a/eth2/utils/tree_hash/src/cached_tree_hash/resize.rs b/eth2/utils/tree_hash/src/cached_tree_hash/resize.rs
index 44b3f0ea5..c87746654 100644
--- a/eth2/utils/tree_hash/src/cached_tree_hash/resize.rs
+++ b/eth2/utils/tree_hash/src/cached_tree_hash/resize.rs
@@ -1,4 +1,5 @@
 use super::*;
+use std::cmp::min;
 
 /// New vec is bigger than old vec.
 pub fn grow_merkle_cache(
@@ -100,8 +101,15 @@ pub fn shrink_merkle_cache(
             )
         };
 
-        to_byte_slice.copy_from_slice(from_byte_slice.get(0..to_byte_slice.len())?);
-        to_flag_slice.copy_from_slice(from_flag_slice.get(0..to_flag_slice.len())?);
+        let num_bytes = min(from_byte_slice.len(), to_byte_slice.len());
+        let num_flags = min(from_flag_slice.len(), to_flag_slice.len());
+
+        to_byte_slice
+            .get_mut(0..num_bytes)?
+            .copy_from_slice(from_byte_slice.get(0..num_bytes)?);
+        to_flag_slice
+            .get_mut(0..num_flags)?
+            .copy_from_slice(from_flag_slice.get(0..num_flags)?);
     }
 
     Some((bytes, flags))
diff --git a/eth2/utils/tree_hash/tests/tests.rs b/eth2/utils/tree_hash/tests/tests.rs
index 726ce5626..27a20cd77 100644
--- a/eth2/utils/tree_hash/tests/tests.rs
+++ b/eth2/utils/tree_hash/tests/tests.rs
@@ -163,7 +163,7 @@ fn test_vec() {
 }
 
 #[test]
-fn test_nested_list() {
+fn test_nested_list_of_u64() {
     let original: Vec<Vec<u64>> = vec![vec![1]];
 
     let modified = vec![
@@ -175,6 +175,8 @@ fn test_nested_list() {
         vec![],
         vec![vec![1, 2], vec![3], vec![4, 5, 6, 7, 8]],
         vec![],
+        vec![vec![1], vec![2], vec![3]],
+        vec![vec![1, 2, 3, 4, 5, 6], vec![1, 2, 3, 4, 5, 6, 7]],
     ];
 
     test_routine(original, modified);