diff --git a/AFNetworking/AFRestClient.m b/AFNetworking/AFRestClient.m
index c207cab..2d81509 100644
--- a/AFNetworking/AFRestClient.m
+++ b/AFNetworking/AFRestClient.m
@@ -106,7 +106,7 @@ static NSStringEncoding const kAFRestClientStringEncoding = NSUTF8StringEncoding
     if (parameters) {
         NSMutableArray *mutableParameterComponents = [NSMutableArray array];
         for (id key in [parameters allKeys]) {
-            NSString *component = [NSString stringWithFormat:@"%@=%@", [key urlEncodedStringWithEncoding:kAFRestClientStringEncoding], [[parameters valueForKey:key] urlEncodedStringWithEncoding:kAFRestClientStringEncoding]];
+            NSString *component = [NSString stringWithFormat:@"%@=%@", [[key description] urlEncodedStringWithEncoding:kAFRestClientStringEncoding], [[[parameters valueForKey:key] description] urlEncodedStringWithEncoding:kAFRestClientStringEncoding]];
             [mutableParameterComponents addObject:component];
         }
         NSString *queryString = [mutableParameterComponents componentsJoinedByString:@"&"];