diff --git a/GCDWebServer.xcodeproj/project.pbxproj b/GCDWebServer.xcodeproj/project.pbxproj
index bfd8815..0729bba 100644
--- a/GCDWebServer.xcodeproj/project.pbxproj
+++ b/GCDWebServer.xcodeproj/project.pbxproj
@@ -1224,6 +1224,7 @@
 					"-Wshadow",
 					"-Wshorten-64-to-32",
 					"-Wstrict-prototypes",
+					"-Wdeprecated-declarations",
 					"-Wno-vla",
 					"-Wno-explicit-ownership-type",
 					"-Wno-gnu-statement-expression",
diff --git a/GCDWebServer/Core/GCDWebServer.m b/GCDWebServer/Core/GCDWebServer.m
index b6a849f..ae9cd14 100644
--- a/GCDWebServer/Core/GCDWebServer.m
+++ b/GCDWebServer/Core/GCDWebServer.m
@@ -415,10 +415,14 @@ static inline id _GetOption(NSDictionary<NSString*, id>* options, NSString* key,
 
 static inline NSString* _EncodeBase64(NSString* string) {
   NSData* data = [string dataUsingEncoding:NSUTF8StringEncoding];
-  if (@available(macOS 10.9, iOS 7.0, tvOS 9.0, *)) {
+#if TARGET_OS_IPHONE
+  return [[NSString alloc] initWithData:[data base64EncodedDataWithOptions:0] encoding:NSASCIIStringEncoding];
+#else
+  if (@available(macOS 10.9, *)) {
     return [[NSString alloc] initWithData:[data base64EncodedDataWithOptions:0] encoding:NSASCIIStringEncoding];
   }
   return [data base64Encoding];
+#endif
 }
 
 - (int)_createListeningSocket:(BOOL)useIPv6