diff --git a/CHANGELOG.md b/CHANGELOG.md
index 411bfe56c..13ed72810 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 1.63.5
+
+### Embedded Sass
+
+* Fix a deadlock when running at high concurrency on 32-bit systems.
+
 ## 1.63.4
 
 ### JavaScript API
diff --git a/lib/src/embedded/isolate_dispatcher.dart b/lib/src/embedded/isolate_dispatcher.dart
index 71c4b041a..0fac523ed 100644
--- a/lib/src/embedded/isolate_dispatcher.dart
+++ b/lib/src/embedded/isolate_dispatcher.dart
@@ -3,6 +3,7 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:async';
+import 'dart:ffi';
 import 'dart:io';
 import 'dart:isolate';
 import 'dart:typed_data';
@@ -51,9 +52,10 @@ class IsolateDispatcher {
   /// A pool controlling how many isolates (and thus concurrent compilations)
   /// may be live at once.
   ///
-  /// More than 15 concurrent `waitFor()` calls seems to deadlock the Dart VM,
-  /// even across isolates. See sass/dart-sass#1959.
-  final _isolatePool = Pool(15);
+  /// More than MaxMutatorThreadCount isolates in the same isolate group
+  /// can deadlock the Dart VM.
+  /// See https://github.com/sass/dart-sass/pull/2019
+  final _isolatePool = Pool(sizeOf<IntPtr>() <= 4 ? 7 : 15);
 
   /// Whether the underlying channel has closed and the dispatcher is shutting
   /// down.
diff --git a/pubspec.yaml b/pubspec.yaml
index 17d19a9db..c6da3a2f1 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sass
-version: 1.63.4
+version: 1.63.5-dev
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass