diff --git a/resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolver.java b/resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolver.java
index 8f4776a606..6c512911d0 100644
--- a/resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolver.java
+++ b/resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolver.java
@@ -642,7 +642,7 @@ public class DnsNameResolver extends SimpleNameResolver<InetSocketAddress> {
 
     @Override
     protected void doResolve(InetSocketAddress unresolvedAddress, Promise<InetSocketAddress> promise) throws Exception {
-        final String hostname = IDN.toASCII(unresolvedAddress.getHostString());
+        final String hostname = IDN.toASCII(hostname(unresolvedAddress));
         final int port = unresolvedAddress.getPort();
 
         final DnsNameResolverContext ctx = new DnsNameResolverContext(this, hostname, port, promise);
@@ -650,6 +650,15 @@ public class DnsNameResolver extends SimpleNameResolver<InetSocketAddress> {
         ctx.resolve();
     }
 
+    private static String hostname(InetSocketAddress addr) {
+        // InetSocketAddress.getHostString() is available since Java 7.
+        if (PlatformDependent.javaVersion() < 7) {
+            return addr.getHostName();
+        } else {
+            return addr.getHostString();
+        }
+    }
+
     /**
      * Sends a DNS query with the specified question.
      */