diff --git a/CHANGELOG.md b/CHANGELOG.md
index ce71980..cca6f11 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 1.2.2
+
+* Allow `SourceSpanException.message`, `SourceSpanFormatException.source`, and
+  `SourceSpanWithContext.context` to be overridden in strong mode.
+
 # 1.2.1
 
 * Fix the declared type of `FileSpan.start` and `FileSpan.end`. In 1.2.0 these
diff --git a/lib/src/span_exception.dart b/lib/src/span_exception.dart
index 921e620..6d3448b 100644
--- a/lib/src/span_exception.dart
+++ b/lib/src/span_exception.dart
@@ -6,15 +6,19 @@
 
 /// A class for exceptions that have source span information attached.
 class SourceSpanException implements Exception {
+  // This is a getter so that subclasses can override it.
   /// A message describing the exception.
-  final String message;
+  String get message => _message;
+  final String _message;
 
+  // This is a getter so that subclasses can override it.
   /// The span associated with this exception.
   ///
   /// This may be `null` if the source location can't be determined.
-  final SourceSpan span;
+  SourceSpan get span => _span;
+  final SourceSpan _span;
 
-  SourceSpanException(this.message, this.span);
+  SourceSpanException(this._message, this._span);
 
   /// Returns a string representation of [this].
   ///
@@ -32,10 +36,9 @@
 /// A [SourceSpanException] that's also a [FormatException].
 class SourceSpanFormatException extends SourceSpanException
     implements FormatException {
-  final _source;
-
-  // Subclasses may narrow the type.
+  // This is a getter so that subclasses can override it.
   dynamic get source => _source;
+  final _source;
 
   int get offset => span == null ? null : span.start.offset;
 
diff --git a/lib/src/span_with_context.dart b/lib/src/span_with_context.dart
index 1336b12..a02d780 100644
--- a/lib/src/span_with_context.dart
+++ b/lib/src/span_with_context.dart
@@ -8,8 +8,10 @@
 
 /// A class that describes a segment of source text with additional context.
 class SourceSpanWithContext extends SourceSpanBase {
+  // This is a getter so that subclasses can override it.
   /// Text around the span, which includes the line containing this span.
-  final String context;
+  String get context => _context;
+  final String _context;
 
   /// Creates a new span from [start] to [end] (exclusive) containing [text], in
   /// the given [context].
@@ -20,7 +22,7 @@
   /// [text] should start at `start.column` from the beginning of a line in
   /// [context].
   SourceSpanWithContext(
-      SourceLocation start, SourceLocation end, String text, this.context)
+          SourceLocation start, SourceLocation end, String text, this._context)
       : super(start, end, text) {
     if (!context.contains(text)) {
       throw new ArgumentError(
diff --git a/pubspec.yaml b/pubspec.yaml
index 4c703cd..7ca7de4 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: source_span
-version: 1.2.1
+version: 1.2.2
 author: Dart Team <misc@dartlang.org>
 description: A library for identifying source spans and locations.
 homepage: https://github.com/dart-lang/source_span