diff --git a/htrace-core/pom.xml b/htrace-core/pom.xml
index 1685a58..120ce7b 100644
--- a/htrace-core/pom.xml
+++ b/htrace-core/pom.xml
@@ -18,7 +18,7 @@
   <parent>
     <artifactId>htrace</artifactId>
     <groupId>org.htrace</groupId>
-    <version>3.0.3</version>
+    <version>3.0.3-SNAPSHOT</version>
   </parent>
 
   <name>htrace-core</name>
diff --git a/htrace-core/src/main/java/org/htrace/NullScope.java b/htrace-core/src/main/java/org/htrace/NullScope.java
new file mode 100644
index 0000000..1f90156
--- /dev/null
+++ b/htrace-core/src/main/java/org/htrace/NullScope.java
@@ -0,0 +1,34 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.htrace;
+
+/**
+ * Singleton instance representing an empty {@link TraceScope}.
+ */
+public final class NullScope extends TraceScope {
+
+  public static final TraceScope INSTANCE = new NullScope();
+
+  private NullScope() {
+    super(null, null);
+  }
+
+  @Override
+  public String toString() {
+    return "NullScope";
+  }
+}
diff --git a/htrace-core/src/main/java/org/htrace/Trace.java b/htrace-core/src/main/java/org/htrace/Trace.java
index 4c14b14..8b1255b 100644
--- a/htrace-core/src/main/java/org/htrace/Trace.java
+++ b/htrace-core/src/main/java/org/htrace/Trace.java
@@ -91,9 +91,8 @@
    * Pick up an existing span from another thread.
    */
   public static TraceScope continueSpan(Span s) {
-    // Return an empty TraceScope that does nothing on
-    // close
-    if (s == null) return new TraceScope(null, null);
+    // Return an empty TraceScope that does nothing on close
+    if (s == null) return NullScope.INSTANCE;
     return Tracer.getInstance().continueSpan(s);
   }
 
diff --git a/htrace-core/src/main/java/org/htrace/TraceScope.java b/htrace-core/src/main/java/org/htrace/TraceScope.java
index 07b7929..f001c52 100644
--- a/htrace-core/src/main/java/org/htrace/TraceScope.java
+++ b/htrace-core/src/main/java/org/htrace/TraceScope.java
@@ -61,6 +61,14 @@
     return span;
   }
 
+  /**
+   * Return true when {@link #detach()} has been called. Helpful when debugging
+   * multiple threads working on a single span.
+   */
+  public boolean isDetached() {
+    return detached;
+  }
+
   @Override
   public void close() {
     if (span == null) return;
diff --git a/htrace-core/src/main/java/org/htrace/Tracer.java b/htrace-core/src/main/java/org/htrace/Tracer.java
index bf69afc..ac31165 100644
--- a/htrace-core/src/main/java/org/htrace/Tracer.java
+++ b/htrace-core/src/main/java/org/htrace/Tracer.java
@@ -91,6 +91,9 @@
   }
 
   protected Span setCurrentSpan(Span span) {
+    if (LOG.isTraceEnabled()) {
+      LOG.trace("setting current span " + span);
+    }
     currentSpan.set(span);
     return span;
   }
@@ -119,4 +122,4 @@
     }
     return processId;
   }
-}
\ No newline at end of file
+}
diff --git a/htrace-core/src/main/java/org/htrace/impl/MilliSpan.java b/htrace-core/src/main/java/org/htrace/impl/MilliSpan.java
index 0d47a40..39c9671 100644
--- a/htrace-core/src/main/java/org/htrace/impl/MilliSpan.java
+++ b/htrace-core/src/main/java/org/htrace/impl/MilliSpan.java
@@ -91,10 +91,7 @@
 
   @Override
   public String toString() {
-    return "start=" + start + "\nstop=" + stop + "\nparentId=" + parentSpanId
-        + "\ndescription=" + description + "\nspanId=" + spanId + "\ntraceId=" + traceId
-        + "\ntraceInfo=" + traceInfo + "\nprocessId=" + processId
-        + "\ntimeline=" + timeline;
+    return String.format("Span{Id:0x%16x,parentId:0x%16x,desc:%s}", spanId, parentSpanId, description);
   }
 
   @Override
@@ -161,4 +158,4 @@
   public String getProcessId() {
     return processId;
   }
-}
\ No newline at end of file
+}
diff --git a/htrace-zipkin/pom.xml b/htrace-zipkin/pom.xml
index 6f1f324..e68f1c2 100644
--- a/htrace-zipkin/pom.xml
+++ b/htrace-zipkin/pom.xml
@@ -18,7 +18,7 @@
   <parent>
     <artifactId>htrace</artifactId>
     <groupId>org.htrace</groupId>
-    <version>3.0.3</version>
+    <version>3.0.3-SNAPSHOT</version>
   </parent>
 
   <name>htrace-zipkin</name>
diff --git a/pom.xml b/pom.xml
index 24e4e63..41a2e66 100644
--- a/pom.xml
+++ b/pom.xml
@@ -14,7 +14,7 @@
 
   <groupId>org.htrace</groupId>
   <artifactId>htrace</artifactId>
-  <version>3.0.3</version>
+  <version>3.0.3-SNAPSHOT</version>
   <packaging>pom</packaging>
 
   <name>htrace</name>