diff --git a/CHANGELOG.md b/CHANGELOG.md
index 226f33eac..dbd93ae38 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Fixes
+
+* Missing OS context for iOS events ([#958](https://github.com/getsentry/sentry-dart/pull/958))
+
 ### Features
 
 * Dio Integration adds response data ([#934](https://github.com/getsentry/sentry-dart/pull/934))
diff --git a/flutter/lib/src/default_integrations.dart b/flutter/lib/src/default_integrations.dart
index 4587a78ff..3fc708dcf 100644
--- a/flutter/lib/src/default_integrations.dart
+++ b/flutter/lib/src/default_integrations.dart
@@ -185,10 +185,19 @@ class _LoadContextsIntegrationEventProcessor extends EventProcessor {
         contexts.forEach(
           (key, dynamic value) {
             if (value != null) {
+              final currentValue = eventContexts[key];
               if (key == SentryRuntime.listType) {
                 contexts.runtimes.forEach(eventContexts.addRuntime);
-              } else if (eventContexts[key] == null) {
+              } else if (currentValue == null) {
                 eventContexts[key] = value;
+              } else {
+                if (key == SentryOperatingSystem.type &&
+                    currentValue is SentryOperatingSystem &&
+                    value is SentryOperatingSystem) {
+                  final osMap = {...value.toJson(), ...currentValue.toJson()};
+                  final os = SentryOperatingSystem.fromJson(osMap);
+                  eventContexts[key] = os;
+                }
               }
             }
           },
diff --git a/flutter/test/load_contexts_integrations_test.dart b/flutter/test/load_contexts_integrations_test.dart
index 7dfc95a8d..2c6b9fd00 100644
--- a/flutter/test/load_contexts_integrations_test.dart
+++ b/flutter/test/load_contexts_integrations_test.dart
@@ -75,12 +75,14 @@ void main() {
     expect(fixture.options.eventProcessors.length, 1);
 
     final e = SentryEvent();
+    e.contexts.operatingSystem = SentryOperatingSystem(theme: 'theme1');
     final event = await fixture.options.eventProcessors.first.apply(e);
 
     expect(fixture.called, true);
     expect(event?.contexts.device?.name, 'Device1');
     expect(event?.contexts.app?.name, 'test-app');
     expect(event?.contexts.operatingSystem?.name, 'os1');
+    expect(event?.contexts.operatingSystem?.theme, 'theme1');
     expect(event?.contexts.gpu?.name, 'gpu1');
     expect(event?.contexts.browser?.name, 'browser1');
     expect(