diff --git a/src/debugger.cc b/src/debugger.cc
index eb5efa2..29cb965 100644
--- a/src/debugger.cc
+++ b/src/debugger.cc
@@ -732,9 +732,13 @@
   return JDWP::ERR_NONE;
 }
 
-uint8_t Dbg::GetObjectTag(JDWP::ObjectId objectId) {
+JDWP::JdwpError Dbg::GetObjectTag(JDWP::ObjectId objectId, uint8_t& tag) {
   Object* o = gRegistry->Get<Object*>(objectId);
-  return TagFromObject(o);
+  if (o == kInvalidObject) {
+    return JDWP::ERR_INVALID_OBJECT;
+  }
+  tag = TagFromObject(o);
+  return JDWP::ERR_NONE;
 }
 
 size_t Dbg::GetTagWidth(JDWP::JdwpTag tag) {
@@ -1543,7 +1547,9 @@
     LOG(WARNING) << "No such thread for resume: " << peer;
     return;
   }
-  Runtime::Current()->GetThreadList()->Resume(thread, true);
+  if (thread->GetSuspendCount() > 0) {
+    Runtime::Current()->GetThreadList()->Resume(thread, true);
+  }
 }
 
 void Dbg::SuspendSelf() {
diff --git a/src/debugger.h b/src/debugger.h
index 89aac8e..9dffa7c 100644
--- a/src/debugger.h
+++ b/src/debugger.h
@@ -141,7 +141,7 @@
   static JDWP::JdwpError GetReferenceType(JDWP::ObjectId objectId, JDWP::ExpandBuf* pReply);
   static JDWP::JdwpError GetSignature(JDWP::RefTypeId refTypeId, std::string& signature);
   static JDWP::JdwpError GetSourceFile(JDWP::RefTypeId refTypeId, std::string& source_file);
-  static uint8_t GetObjectTag(JDWP::ObjectId objectId);
+  static JDWP::JdwpError GetObjectTag(JDWP::ObjectId objectId, uint8_t& tag);
   static size_t GetTagWidth(JDWP::JdwpTag tag);
 
   static JDWP::JdwpError GetArrayLength(JDWP::ObjectId arrayId, int& length);
diff --git a/src/jdwp/jdwp_handler.cc b/src/jdwp/jdwp_handler.cc
index c49e9da..05fc979 100644
--- a/src/jdwp/jdwp_handler.cc
+++ b/src/jdwp/jdwp_handler.cc
@@ -974,16 +974,16 @@
 
   expandBufAdd4BE(pReply, length);
   for (uint32_t i = start_frame; i < (start_frame + length); ++i) {
-    FrameId frameId;
+    FrameId frame_id;
     JdwpLocation loc;
     // TODO: switch to GetThreadFrames so we don't have to search for each frame
     // even though we only want them in order.
-    Dbg::GetThreadFrame(threadId, i, &frameId, &loc);
+    Dbg::GetThreadFrame(threadId, i, &frame_id, &loc);
 
-    expandBufAdd8BE(pReply, frameId);
+    expandBufAdd8BE(pReply, frame_id);
     AddLocation(pReply, &loc);
 
-    VLOG(jdwp) << StringPrintf("    Frame %d: id=%#llx ", i, frameId) << loc;
+    VLOG(jdwp) << StringPrintf("    Frame %d: id=%#llx ", i, frame_id) << loc;
   }
 
   return ERR_NONE;
@@ -1339,10 +1339,10 @@
  */
 static JdwpError handleSF_GetValues(JdwpState*, const uint8_t* buf, int, ExpandBuf* pReply) {
   ObjectId threadId = ReadObjectId(&buf);
-  FrameId frameId = ReadFrameId(&buf);
+  FrameId frame_id = ReadFrameId(&buf);
   uint32_t slots = Read4BE(&buf);
 
-  VLOG(jdwp) << StringPrintf("  Req for %d slots in threadId=%#llx frameId=%#llx", slots, threadId, frameId);
+  VLOG(jdwp) << StringPrintf("  Req for %d slots in threadId=%#llx frame_id=%#llx", slots, threadId, frame_id);
 
   expandBufAdd4BE(pReply, slots);     /* "int values" */
   for (uint32_t i = 0; i < slots; i++) {
@@ -1353,7 +1353,7 @@
 
     size_t width = Dbg::GetTagWidth(reqSigByte);
     uint8_t* ptr = expandBufAddSpace(pReply, width+1);
-    Dbg::GetLocalValue(threadId, frameId, slot, reqSigByte, ptr, width);
+    Dbg::GetLocalValue(threadId, frame_id, slot, reqSigByte, ptr, width);
   }
 
   return ERR_NONE;
@@ -1364,10 +1364,10 @@
  */
 static JdwpError handleSF_SetValues(JdwpState*, const uint8_t* buf, int, ExpandBuf*) {
   ObjectId threadId = ReadObjectId(&buf);
-  FrameId frameId = ReadFrameId(&buf);
+  FrameId frame_id = ReadFrameId(&buf);
   uint32_t slots = Read4BE(&buf);
 
-  VLOG(jdwp) << StringPrintf("  Req to set %d slots in threadId=%#llx frameId=%#llx", slots, threadId, frameId);
+  VLOG(jdwp) << StringPrintf("  Req to set %d slots in threadId=%#llx frame_id=%#llx", slots, threadId, frame_id);
 
   for (uint32_t i = 0; i < slots; i++) {
     uint32_t slot = Read4BE(&buf);
@@ -1376,7 +1376,7 @@
     uint64_t value = jdwpReadValue(&buf, width);
 
     VLOG(jdwp) << "    --> slot " << slot << " " << sigByte << " " << value;
-    Dbg::SetLocalValue(threadId, frameId, slot, sigByte, value, width);
+    Dbg::SetLocalValue(threadId, frame_id, slot, sigByte, value, width);
   }
 
   return ERR_NONE;
@@ -1387,16 +1387,20 @@
  */
 static JdwpError handleSF_ThisObject(JdwpState*, const uint8_t* buf, int, ExpandBuf* pReply) {
   ReadObjectId(&buf); // Skip thread id.
-  FrameId frameId = ReadFrameId(&buf);
+  FrameId frame_id = ReadFrameId(&buf);
 
-  ObjectId objectId;
-  Dbg::GetThisObject(frameId, &objectId);
+  ObjectId id;
+  Dbg::GetThisObject(frame_id, &id);
 
-  uint8_t objectTag = Dbg::GetObjectTag(objectId);
-  VLOG(jdwp) << StringPrintf("  Req for 'this' in frame=%#llx --> %#llx '%c'", frameId, objectId, (char)objectTag);
+  uint8_t tag;
+  JdwpError result = Dbg::GetObjectTag(id, tag);
+  if (result != ERR_NONE) {
+    return result;
+  }
 
-  expandBufAdd1(pReply, objectTag);
-  expandBufAddObjectId(pReply, objectId);
+  VLOG(jdwp) << StringPrintf("  Req for 'this' in frame=%#llx --> %#llx '%c'", frame_id, id, static_cast<char>(tag));
+  expandBufAdd1(pReply, tag);
+  expandBufAddObjectId(pReply, id);
 
   return ERR_NONE;
 }
diff --git a/src/thread_list.cc b/src/thread_list.cc
index 186ddbc..951a2be 100644
--- a/src/thread_list.cc
+++ b/src/thread_list.cc
@@ -274,7 +274,7 @@
     MutexLock mu(thread_suspend_count_lock_);
     for (It it = list_.begin(), end = list_.end(); it != end; ++it) {
       Thread* thread = *it;
-      if (thread == self || (for_debugger && thread == debug_thread)) {
+      if (thread == self || (for_debugger && thread == debug_thread) || thread->suspend_count_ == 0) {
         continue;
       }
       ModifySuspendCount(thread, -1, for_debugger);