diff --git a/Package.swift b/Package.swift
index 563bdfdde..63a801ac4 100644
--- a/Package.swift
+++ b/Package.swift
@@ -20,14 +20,28 @@ import PackageDescription
        limitations under the License.
 */
 
+var platforms: [SupportedPlatform] {
+    #if compiler(<5.3)
+        return [
+            .macOS(.v10_10),
+            .iOS(.v8),
+            .tvOS(.v9),
+            .watchOS(.v2),
+        ]
+    #else
+        // Xcode 12 (which ships with Swift 5.3) drops support for iOS 8
+        return [
+            .macOS(.v10_10),
+            .iOS(.v9),
+            .tvOS(.v9),
+            .watchOS(.v2),
+        ]
+    #endif
+}
+
 let package = Package(
     name: "AppAuth",
-    platforms: [
-        .macOS(.v10_10),
-        .iOS(.v8),
-        .tvOS(.v9),
-        .watchOS(.v2)
-    ],
+    platforms: platforms,
     products: [
         .library(
             name: "AppAuthCore",
diff --git a/Source/AppAuth/iOS/OIDExternalUserAgentIOS.m b/Source/AppAuth/iOS/OIDExternalUserAgentIOS.m
index 728f0868d..be20b9af1 100644
--- a/Source/AppAuth/iOS/OIDExternalUserAgentIOS.m
+++ b/Source/AppAuth/iOS/OIDExternalUserAgentIOS.m
@@ -163,10 +163,17 @@ - (BOOL)presentExternalUserAgentRequest:(id<OIDExternalUserAgentRequest>)request
       openedUserAgent = YES;
     }
   }
-  // iOS 8 and earlier, use mobile Safari
-  if (!openedUserAgent){
-    openedUserAgent = [[UIApplication sharedApplication] openURL:requestURL];
-  }
+// Xcode 13 beta 3 introduces a breaking change for APIs marked unavailable for iOS extensions
+// https://developer.apple.com/documentation/xcode-release-notes/xcode-13-beta-release-notes
+// The solution is to annotate apis that depend on APIs marked unavailable (sharedApplication, openURL).
+// An easier solution is to remove those APIs in the first place.
+// less than iOS 15, on Xcode 13
+#if __IPHONE_OS_VERSION_MAX_ALLOWED < 150000
+    // iOS 8 and earlier, use mobile Safari
+    if (!openedUserAgent){
+      openedUserAgent = [[UIApplication sharedApplication] openURL:requestURL];
+    }
+#endif
 
   if (!openedUserAgent) {
     [self cleanUp];