diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2dd056929..7ab247d4d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+## 1.45.3
+
+### JS API
+
+* **Potentially breaking bug fix:** Match the specification of the new JS API by
+  passing `undefined` rather than `null` to `Logger.warn()` for an unset `span`.
+
 ## 1.45.2
 
 ### JS API
diff --git a/lib/src/logger/node_to_dart.dart b/lib/src/logger/node_to_dart.dart
index 93a0a4b3e..bb16798fc 100644
--- a/lib/src/logger/node_to_dart.dart
+++ b/lib/src/logger/node_to_dart.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import 'package:node_interop/js.dart';
 import 'package:source_span/source_span.dart';
 import 'package:stack_trace/stack_trace.dart';
 import 'package:term_glyph/term_glyph.dart' as glyph;
@@ -38,7 +39,9 @@ class NodeToDartLogger implements Logger {
       warn(
           message,
           WarnOptions(
-              span: span, stack: trace.toString(), deprecation: deprecation));
+              span: span ?? (undefined as SourceSpan?),
+              stack: trace.toString(),
+              deprecation: deprecation));
     }
   }
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 2bd409d5d..96a16cc63 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sass
-version: 1.45.2
+version: 1.45.3
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass