diff --git a/CHANGELOG.md b/CHANGELOG.md
index 022f12028de6a..d5847334c4539 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+## 3.1.1
+
+- Make `isInKeepAlive` on `SseConnection` private.
+
+**Note that this is a breaking change but in actuality no one should be
+  depending on this API.**
+
 ## 3.1.0
 
 - Add optional `keepAlive` parameter to the `SseHandler`. If `keepAlive` is
@@ -9,8 +16,8 @@
 
 - Add retry logic.
 
-** Possible Breaking Change ** Error messages may now be delayed up to 5 seconds
-in the client.
+**Possible Breaking Change Error messages may now be delayed up to 5 seconds
+  in the client.**
 
 ## 2.1.2
 
diff --git a/lib/src/server/sse_handler.dart b/lib/src/server/sse_handler.dart
index e8cd523b93277..9c3d91eb0eb03 100644
--- a/lib/src/server/sse_handler.dart
+++ b/lib/src/server/sse_handler.dart
@@ -37,7 +37,7 @@ class SseConnection extends StreamChannelMixin<String> {
   Timer _keepAliveTimer;
 
   /// Whether this connection is currently in the KeepAlive timeout period.
-  bool get isInKeepAlivePeriod => _keepAliveTimer?.isActive ?? false;
+  bool get _isInKeepAlivePeriod => _keepAliveTimer?.isActive ?? false;
 
   final _closedCompleter = Completer<void>();
 
@@ -60,7 +60,7 @@ class SseConnection extends StreamChannelMixin<String> {
     while (await outgoingStreamQueue.hasNext) {
       // If we're in a KeepAlive timeout, there's nowhere to send messages so
       // wait a short period and check again.
-      if (isInKeepAlivePeriod) {
+      if (_isInKeepAlivePeriod) {
         await Future.delayed(const Duration(milliseconds: 200));
         continue;
       }
@@ -105,7 +105,7 @@ class SseConnection extends StreamChannelMixin<String> {
     if (_keepAlive == null) {
       // Close immediately if we're not keeping alive.
       _close();
-    } else if (!isInKeepAlivePeriod) {
+    } else if (!_isInKeepAlivePeriod) {
       // Otherwise if we didn't already have an active timer, set a timer to
       // close after the timeout period. If the connection comes back, this will
       // be cancelled and all messages left in the queue tried again.
@@ -155,7 +155,7 @@ class SseHandler {
       // Check if we already have a connection for this ID that is in the process
       // of timing out (in which case we can reconnect it transparently).
       if (_connections[clientId] != null &&
-          _connections[clientId].isInKeepAlivePeriod) {
+          _connections[clientId]._isInKeepAlivePeriod) {
         _connections[clientId]._acceptReconnection(sink);
       } else {
         var connection = SseConnection(sink, keepAlive: _keepAlive);
diff --git a/pubspec.yaml b/pubspec.yaml
index 9c164f79e7ce8..52d69e5f2411e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sse
-version: 3.1.0
+version: 3.1.1
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/sse
 description: >-