diff --git a/AppAuth.podspec b/AppAuth.podspec
index bfffe6cda..0dd7f508b 100644
--- a/AppAuth.podspec
+++ b/AppAuth.podspec
@@ -31,7 +31,7 @@ It follows the OAuth 2.0 for Native Apps best current practice
   #       classes of AppAuth with tokens on watchOS and tvOS, but currently the
   #       library won't help you obtain authorization grants on those platforms.
 
-  ios_deployment_target = "9.0"
+  ios_deployment_target = "15.0"
   osx_deployment_target = "10.12"
   s.ios.deployment_target = ios_deployment_target
   s.osx.deployment_target = osx_deployment_target
diff --git a/AppAuth.xcodeproj/project.pbxproj b/AppAuth.xcodeproj/project.pbxproj
index 8d770d93c..c6ebc051b 100644
--- a/AppAuth.xcodeproj/project.pbxproj
+++ b/AppAuth.xcodeproj/project.pbxproj
@@ -2815,7 +2815,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.12;
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
@@ -2873,7 +2873,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.12;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
@@ -2907,7 +2907,6 @@
 				CLANG_ENABLE_MODULES = YES;
 				HEADER_SEARCH_PATHS = "$(PROJECT_DIR)/";
 				INFOPLIST_FILE = UnitTests/UnitTestsInfo.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = net.openid.appauth.AppAuthTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -2924,7 +2923,6 @@
 				CLANG_ENABLE_MODULES = YES;
 				HEADER_SEARCH_PATHS = "$(PROJECT_DIR)/";
 				INFOPLIST_FILE = UnitTests/UnitTestsInfo.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = net.openid.appauth.AppAuthTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -3038,7 +3036,6 @@
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				INFOPLIST_FILE = Sources/CoreFramework/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = net.openid.AppAuthCore;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -3064,7 +3061,6 @@
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				INFOPLIST_FILE = Sources/CoreFramework/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = net.openid.AppAuthCore;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -3089,7 +3085,6 @@
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				INFOPLIST_FILE = Sources/Framework/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "net.openid.AppAuth-iOS";
 				PRODUCT_NAME = AppAuth;
@@ -3114,7 +3109,6 @@
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				INFOPLIST_FILE = Sources/Framework/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "net.openid.AppAuth-iOS";
 				PRODUCT_NAME = AppAuth;
@@ -3133,7 +3127,6 @@
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				HEADER_SEARCH_PATHS = .;
 				INFOPLIST_FILE = UnitTests/UnitTestsInfo.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "net.openid.AppAuth-iOSTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -3147,7 +3140,6 @@
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				HEADER_SEARCH_PATHS = .;
 				INFOPLIST_FILE = UnitTests/UnitTestsInfo.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "net.openid.AppAuth-iOSTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -3401,7 +3393,6 @@
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				HEADER_SEARCH_PATHS = .;
 				INFOPLIST_FILE = UnitTests/UnitTestsInfo.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "net.openid.AppAuth-ExtensionTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -3415,7 +3406,6 @@
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				HEADER_SEARCH_PATHS = .;
 				INFOPLIST_FILE = UnitTests/UnitTestsInfo.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "net.openid.AppAuth-ExtensionTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
diff --git a/Package.swift b/Package.swift
index 103c0f761..94c96303c 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:5.3
+// swift-tools-version:5.9
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 import PackageDescription
 
@@ -24,7 +24,7 @@ let package = Package(
     name: "AppAuth",
     platforms: [
         .macOS(.v10_12),
-        .iOS(.v9),
+        .iOS(.v15),
         .tvOS(.v9),
         .watchOS(.v2)
     ],