diff --git a/OpenVPN Adapter/OpenVPNAdapter.mm b/OpenVPN Adapter/OpenVPNAdapter.mm
index f208fd8..554e669 100644
--- a/OpenVPN Adapter/OpenVPNAdapter.mm	
+++ b/OpenVPN Adapter/OpenVPNAdapter.mm	
@@ -565,9 +565,7 @@ static void socketCallback(CFSocketRef socket, CFSocketCallBackType type, CFData
             
 #if TARGET_OS_IPHONE
             // Prepend data with network protocol. It should be done because OpenVPN on iOS uses uint32_t prefixes containing network protocol.
-            NSNumber *protocol = protocols[idx];
-            uint32_t prefix = CFSwapInt32HostToBig((uint32_t)[protocol unsignedIntegerValue]);
-            
+            uint32_t prefix = CFSwapInt32HostToBig([self getProtocolVersion:[protocols[idx] unsignedCharValue]]);
             [packet appendBytes:&prefix length:sizeof(prefix)];
 #endif
             
@@ -695,6 +693,14 @@ static void socketCallback(CFSocketRef socket, CFSocketCallBackType type, CFData
         default: return PF_UNSPEC;
     }
 }
+
+- (uint32_t)getProtocolVersion:(uint8_t)family {
+    switch (family) {
+        case PF_INET: return 4;
+        case PF_INET6: return 6;
+        default: return 0;
+    }
+}
     
 - (void)performAsyncBlock:(void (^)())block {
     dispatch_queue_t mainQueue = dispatch_get_main_queue();