diff --git a/arrow-cast/src/cast/dictionary.rs b/arrow-cast/src/cast/dictionary.rs
index 0092bc0c87dd..601f50a4d001 100644
--- a/arrow-cast/src/cast/dictionary.rs
+++ b/arrow-cast/src/cast/dictionary.rs
@@ -361,22 +361,18 @@ where
     D: DecimalType + ArrowPrimitiveType,
 {
     let dict = pack_numeric_to_dictionary::<K, D>(array, dict_value_type, cast_options)?;
-    let dict = dict
-        .as_dictionary::<K>()
-        .downcast_dict::<PrimitiveArray<D>>()
-        .ok_or_else(|| {
-            ArrowError::ComputeError(format!(
-                "Internal Error: Cannot cast dict to {}Array",
-                D::PREFIX
-            ))
-        })?;
-    let value = dict.values().clone();
-    // Set correct precision/scale
-    let value = value.with_precision_and_scale(precision, scale)?;
-    Ok(Arc::new(DictionaryArray::<K>::try_new(
-        dict.keys().clone(),
-        Arc::new(value),
-    )?))
+    let dict = dict.as_dictionary::<K>();
+    let typed = dict.downcast_dict::<PrimitiveArray<D>>().ok_or_else(|| {
+        ArrowError::ComputeError(format!(
+            "Internal Error: Cannot cast dict to {}Array",
+            D::PREFIX
+        ))
+    })?;
+    let value = typed
+        .values()
+        .clone()
+        .with_precision_and_scale(precision, scale)?;
+    Ok(Arc::new(dict.with_values(Arc::new(value))))
 }
 
 pub(crate) fn string_view_to_dictionary<K, O: OffsetSizeTrait>(
diff --git a/arrow-string/src/substring.rs b/arrow-string/src/substring.rs
index 05b3888a444a..3dc3bd695c44 100644
--- a/arrow-string/src/substring.rs
+++ b/arrow-string/src/substring.rs
@@ -86,8 +86,7 @@ pub fn substring(
                                        stringify!($gt), array.data_type())
                             });
                         let values = substring(dict.values(), start, length)?;
-                        let result = DictionaryArray::try_new(dict.keys().clone(), values)?;
-                        Ok(Arc::new(result))
+                        Ok(Arc::new(dict.with_values(values)))
                     },
                 )*
                     t => panic!("Unsupported dictionary key type: {}", t)