diff --git a/eth2/utils/ssz/src/cached_tree_hash/resize.rs b/eth2/utils/ssz/src/cached_tree_hash/resize.rs
index 2cdce4827..3c2d2c407 100644
--- a/eth2/utils/ssz/src/cached_tree_hash/resize.rs
+++ b/eth2/utils/ssz/src/cached_tree_hash/resize.rs
@@ -26,7 +26,7 @@ pub fn grow_merkle_cache(
         // (e.g., the case where there are subtrees as leaves).
         //
         // If we're not on a leaf level, the number of nodes is fixed and known.
-        let (byte_slice, flag_slice) = if i == leaf_level {
+        let (old_byte_slice, old_flag_slice) = if i == leaf_level {
             (
                 old_bytes.get(first_byte_at_height(i)..)?,
                 old_flags.get(first_node_at_height(i)..)?,
@@ -38,14 +38,25 @@ pub fn grow_merkle_cache(
             )
         };
 
-        bytes
-            .get_mut(byte_range_at_height(i + to_height - from_height))?
-            .get_mut(0..byte_slice.len())?
-            .copy_from_slice(byte_slice);
-        flags
-            .get_mut(node_range_at_height(i + to_height - from_height))?
-            .get_mut(0..flag_slice.len())?
-            .copy_from_slice(flag_slice);
+        let new_i = i + to_height - from_height;
+        let (new_byte_slice, new_flag_slice) = if i == leaf_level {
+            (
+                bytes.get_mut(first_byte_at_height(new_i)..)?,
+                flags.get_mut(first_node_at_height(new_i)..)?,
+            )
+        } else {
+            (
+                bytes.get_mut(byte_range_at_height(new_i))?,
+                flags.get_mut(node_range_at_height(new_i))?,
+            )
+        };
+
+        new_byte_slice
+            .get_mut(0..old_byte_slice.len())?
+            .copy_from_slice(old_byte_slice);
+        new_flag_slice
+            .get_mut(0..old_flag_slice.len())?
+            .copy_from_slice(old_flag_slice);
     }
 
     Some((bytes, flags))
diff --git a/eth2/utils/ssz/src/cached_tree_hash/tests.rs b/eth2/utils/ssz/src/cached_tree_hash/tests.rs
index c402fd15b..fb6ed9080 100644
--- a/eth2/utils/ssz/src/cached_tree_hash/tests.rs
+++ b/eth2/utils/ssz/src/cached_tree_hash/tests.rs
@@ -472,9 +472,10 @@ fn test_inner_vec_modifications(original: Vec<Inner>, modified: Vec<Inner>, refe
     }
 
     let num_leaves = leaves.len() / HASHSIZE;
-
     let mut expected = merkleize(leaves);
-    expected.splice(3 * HASHSIZE.., full_bytes);
+
+    let num_internal_nodes = num_leaves.next_power_of_two() - 1;
+    expected.splice(num_internal_nodes * HASHSIZE.., full_bytes);
 
     for _ in num_leaves..num_leaves.next_power_of_two() {
         expected.append(&mut vec![0; HASHSIZE]);
@@ -589,6 +590,48 @@ fn lengthened_vec_of_inner_within_power_of_two_boundary() {
     test_inner_vec_modifications(original, modified, reference_vec);
 }
 
+#[test]
+fn lengthened_vec_of_inner_outside_power_of_two_boundary() {
+    let original = vec![
+        Inner {
+            a: 0,
+            b: 1,
+            c: 2,
+            d: 3,
+        },
+        Inner {
+            a: 4,
+            b: 5,
+            c: 6,
+            d: 7,
+        },
+        Inner {
+            a: 8,
+            b: 9,
+            c: 10,
+            d: 11,
+        },
+        Inner {
+            a: 12,
+            b: 13,
+            c: 14,
+            d: 15,
+        },
+    ];
+
+    let mut modified = original.clone();
+    modified.push(Inner {
+        a: 16,
+        b: 17,
+        c: 18,
+        d: 19,
+    });
+
+    let reference_vec: Vec<u64> = (0..20).collect();
+
+    test_inner_vec_modifications(original, modified, reference_vec);
+}
+
 #[test]
 fn vec_of_inner_builds() {
     let numbers: Vec<u64> = (0..12).collect();