```
diff --git a/core/src/main/java/org/jruby/ext/socket/RubyBasicSocket.java b/core/src/main/java/org/jruby/ext/socket/RubyBasicSocket.java
index 4e7a1a32d1..b46fe315d7 100644
--- a/core/src/main/java/org/jruby/ext/socket/RubyBasicSocket.java
+++ b/core/src/main/java/org/jruby/ext/socket/RubyBasicSocket.java
@@ -442,6 +442,7 @@ public class RubyBasicSocket extends RubyIO {
                             if (ret != 0) {
                                 throw runtime.newErrnoEINVALError(SOCKOPT.strerror(ret));
                             }
+                            len.flip();
                             buf.flip();
                             ByteList bytes = new ByteList(buf.array(), 0, len.get());
```