diff --git a/docs/articles/migrate-to-v2.md b/docs/articles/migrate-to-v2.md
index 9d43a74..e5e6263 100644
--- a/docs/articles/migrate-to-v2.md
+++ b/docs/articles/migrate-to-v2.md
@@ -408,8 +408,8 @@ See [History updates](responses.md#history-updates).
 | `Target`             | `Target`                                                                                      |
 | `Swap`               | `Swap` for a swap style; `SwapExpression` for a style with modifiers                          |
 | `Select`             | `Select`                                                                                      |
-| `Values` (`object`)  | `Values` (`IDictionary<string, HtmxFieldValues>`)                                             |
-| `Headers` (`object`) | `Headers` (`IDictionary<string, string>`)                                                     |
+| `Values` (`object`)  | `Values` (`IReadOnlyDictionary<string, HtmxFieldValues>`)                                     |
+| `Headers` (`object`) | `Headers` (`IReadOnlyDictionary<string, string>`)                                             |
 | `Event`, `Handler`   | Removed: HTMX expects a live browser event and a JavaScript function, which JSON cannot carry |
 | —                    | New: `SelectOob`, `HistoryUrl`, `HistoryAction`                                               |
 
diff --git a/src/Ramstack.HtmxToolkit/HtmxLocationOptions.cs b/src/Ramstack.HtmxToolkit/HtmxLocationOptions.cs
index d5a19af..51eba05 100644
--- a/src/Ramstack.HtmxToolkit/HtmxLocationOptions.cs
+++ b/src/Ramstack.HtmxToolkit/HtmxLocationOptions.cs
@@ -52,7 +52,7 @@ public HtmxSwap? Swap
     ///   HTMX 4.0.0 converts an array to a single comma-separated field value.
     /// </para>
     /// </remarks>
-    public IDictionary<string, HtmxFieldValues>? Values { get; set; }
+    public IReadOnlyDictionary<string, HtmxFieldValues>? Values { get; set; }
 
     /// <summary>
     /// Gets or sets the headers to include with the request.
@@ -66,7 +66,7 @@ public HtmxSwap? Swap
     ///   Pass complex data as a pre-serialized JSON string.
     /// </para>
     /// </remarks>
-    public IDictionary<string, string>? Headers { get; set; }
+    public IReadOnlyDictionary<string, string>? Headers { get; set; }
 
     /// <summary>
     /// Gets or sets a CSS selector used to filter the content to swap from the response.
diff --git a/src/Ramstack.HtmxToolkit/Serialization/HtmxLocationOptionsJsonView.cs b/src/Ramstack.HtmxToolkit/Serialization/HtmxLocationOptionsJsonView.cs
index e29a0ec..7e7f901 100644
--- a/src/Ramstack.HtmxToolkit/Serialization/HtmxLocationOptionsJsonView.cs
+++ b/src/Ramstack.HtmxToolkit/Serialization/HtmxLocationOptionsJsonView.cs
@@ -32,12 +32,12 @@ internal readonly struct HtmxLocationOptionsJsonView(string path, HtmxLocationOp
     /// <summary>
     /// Gets the form field values.
     /// </summary>
-    public IDictionary<string, HtmxFieldValues>? Values => options.Values;
+    public IReadOnlyDictionary<string, HtmxFieldValues>? Values => options.Values;
 
     /// <summary>
     /// Gets the request headers.
     /// </summary>
-    public IDictionary<string, string>? Headers => options.Headers;
+    public IReadOnlyDictionary<string, string>? Headers => options.Headers;
 
     /// <summary>
     /// Gets the content selector.