diff --git a/presto-orc/src/main/java/com/facebook/presto/orc/ChunkedSliceOutput.java b/presto-orc/src/main/java/com/facebook/presto/orc/ChunkedSliceOutput.java
index e21b93e4273c2..e5142bc7a25ec 100644
--- a/presto-orc/src/main/java/com/facebook/presto/orc/ChunkedSliceOutput.java
+++ b/presto-orc/src/main/java/com/facebook/presto/orc/ChunkedSliceOutput.java
@@ -303,9 +303,9 @@ public String toString(Charset charset)
     @Override
     public String toString()
     {
-        StringBuilder builder = new StringBuilder("OutputStreamSliceOutputAdapter{");
+        StringBuilder builder = new StringBuilder("ChunkedSliceOutput{");
         builder.append("position=").append(size());
-        builder.append("bufferSize=").append(slice.length());
+        builder.append(", bufferSize=").append(slice.length());
         builder.append('}');
         return builder.toString();
     }
diff --git a/presto-orc/src/main/java/com/facebook/presto/orc/OrcOutputBuffer.java b/presto-orc/src/main/java/com/facebook/presto/orc/OrcOutputBuffer.java
index 6c87f1c8a6228..21205102016dc 100644
--- a/presto-orc/src/main/java/com/facebook/presto/orc/OrcOutputBuffer.java
+++ b/presto-orc/src/main/java/com/facebook/presto/orc/OrcOutputBuffer.java
@@ -421,9 +421,9 @@ public String toString(Charset charset)
     @Override
     public String toString()
     {
-        StringBuilder builder = new StringBuilder("OutputStreamSliceOutputAdapter{");
+        StringBuilder builder = new StringBuilder("OrcOutputBuffer{");
         builder.append("outputStream=").append(compressedOutputStream);
-        builder.append("bufferSize=").append(slice.length());
+        builder.append(", bufferSize=").append(slice.length());
         builder.append('}');
         return builder.toString();
     }