diff --git a/.changeset/nervous-donuts-relate.md b/.changeset/nervous-donuts-relate.md
new file mode 100644
index 00000000..9345eb71
--- /dev/null
+++ b/.changeset/nervous-donuts-relate.md
@@ -0,0 +1,5 @@
+---
+'react-native-app-auth': patch
+---
+
+#1063 Updated getCustomBrowser: in RNAppAuth.m to explicitly check the return value of browser. If the value is not in the dictionary, it will return nil to trigger an ephemeral session.
diff --git a/.gitignore b/.gitignore
index e545102e..6edaa449 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,6 +33,10 @@ android/gradle/
 android/gradlew
 android/gradlew.bat
 
+# Android/Eclipse
+#
+android/.settings/
+
 # node.js
 #
 node_modules/
diff --git a/packages/react-native-app-auth/ios/RNAppAuth.m b/packages/react-native-app-auth/ios/RNAppAuth.m
index 938c045c..a4afddc6 100644
--- a/packages/react-native-app-auth/ios/RNAppAuth.m
+++ b/packages/react-native-app-auth/ios/RNAppAuth.m
@@ -717,6 +717,9 @@ - (NSString*)getErrorCode: (NSError*) error defaultCode: (NSString *) defaultCod
             }
     };
     BrowserBlock browser = browsers[browserType];
+    if (!browser) {
+        return nil;
+    }
     return browser();
 }
 #endif