diff --git a/pat.cpp b/pat.cpp
index 11f3f5a..f939608 100644
--- a/pat.cpp
+++ b/pat.cpp
@@ -226,17 +226,12 @@ pair<bool, int> DualPatternComposer::nextBatch(PerThreadReadBuf& pt) {
  * Returns pair<bool, int> where bool indicates whether we're
  * completely done, and int indicates how many reads were read.
  */
-pair<bool, int> CFilePatternSource::nextBatch(
+pair<bool, int> CFilePatternSource::nextBatchImpl(
 	PerThreadReadBuf& pt,
-	bool batch_a,
-	bool lock)
+	bool batch_a)
 {
 	bool done = false;
 	int nread = 0;
-	
-	// synchronization at this level because both reading and manipulation of
-	// current file pointer have to be protected
-	ThreadSafe ts(&mutex, lock);
 	pt.setReadId(readCnt_);
 	while(true) { // loop that moves on to next file when needed
 		do {
@@ -259,6 +254,21 @@ pair<bool, int> CFilePatternSource::nextBatch(
 	return make_pair(done, nread);
 }
 
+pair<bool, int> CFilePatternSource::nextBatch(
+	PerThreadReadBuf& pt,
+	bool batch_a,
+	bool lock)
+{
+	if(lock) {
+		// synchronization at this level because both reading and manipulation of
+		// current file pointer have to be protected
+		ThreadSafe ts(&mutex);
+		return nextBatchImpl(pt, batch_a);
+	} else {
+		return nextBatchImpl(pt, batch_a);
+	}
+}
+
 /**
  * Open the next file in the list of input files.
  */
@@ -366,12 +376,10 @@ VectorPatternSource::VectorPatternSource(
  * in the contsructor.  This essentially modifies the pt as though we read
  * in some number of patterns.
  */
-pair<bool, int> VectorPatternSource::nextBatch(
+pair<bool, int> VectorPatternSource::nextBatchImpl(
 	PerThreadReadBuf& pt,
-	bool batch_a,
-	bool lock)
+	bool batch_a)
 {
-	ThreadSafe ts(&mutex, lock);
 	pt.setReadId(cur_);
 	vector<Read>& readbuf = batch_a ? pt.bufa_ : pt.bufb_;
 	size_t readi = 0;
@@ -384,6 +392,19 @@ pair<bool, int> VectorPatternSource::nextBatch(
 	return make_pair(cur_ == bufs_.size(), readi);
 }
 
+pair<bool, int> VectorPatternSource::nextBatch(
+	PerThreadReadBuf& pt,
+	bool batch_a,
+	bool lock)
+{
+	if(lock) {
+		ThreadSafe ts(&mutex);
+		return nextBatchImpl(pt, batch_a);
+	} else {
+		return nextBatchImpl(pt, batch_a);
+	}
+}
+
 /**
  * Finishes parsing outside the critical section.
  */
diff --git a/pat.h b/pat.h
index 6c9420a..01b6b15 100644
--- a/pat.h
+++ b/pat.h
@@ -503,10 +503,10 @@ class VectorPatternSource : public TrimmingPatternSource {
 public:
 	VectorPatternSource(
 		const vector<string>& v,
-	    bool color,
-	    const char *dumpfile = NULL,
-	    int trim3 = 0,
-	    int trim5 = 0);
+		bool color,
+		const char *dumpfile = NULL,
+		int trim3 = 0,
+		int trim5 = 0);
 	
 	virtual ~VectorPatternSource() { }
 	
@@ -537,6 +537,10 @@ class VectorPatternSource : public TrimmingPatternSource {
 
 private:
 
+	pair<bool, int> nextBatchImpl(
+		PerThreadReadBuf& pt,
+		bool batch_a);
+
 	bool color_;                      // colorspace?
 	size_t cur_;                      // index for first read of next batch
 	bool paired_;                     // whether reads are paired
@@ -648,6 +652,13 @@ class CFilePatternSource : public TrimmingPatternSource {
 	bool first_;
 	char buf_[64*1024]; /// file buffer for sequences
 	char qbuf_[64*1024]; /// file buffer for qualities
+
+private:
+
+	pair<bool, int> nextBatchImpl(
+		PerThreadReadBuf& pt,
+		bool batch_a);
+
 };
 
 /**
diff --git a/threading.h b/threading.h
index 30ebd2d..a5cf944 100644
--- a/threading.h
+++ b/threading.h
@@ -5,6 +5,7 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <cassert>
 
 #ifdef WITH_TBB
 # include <tbb/mutex.h>
@@ -54,35 +55,32 @@ struct thread_tracking_pair {
 class ThreadSafe {
 public:
 
-	ThreadSafe() : ptr_mutex(NULL) { }
-	
-	ThreadSafe(MUTEX_T* ptr_mutex, bool locked = true) : ptr_mutex(NULL) {
-		if(locked) {
+	ThreadSafe(MUTEX_T* ptr_mutex) :
 #if WITH_TBB && NO_SPINLOCK && WITH_QUEUELOCK
-			//have to use the heap as we can't copy
-			//the scoped lock
-			this->ptr_mutex = new MUTEX_T::scoped_lock(*ptr_mutex);
+		mutex_(*ptr_mutex)
 #else
-			this->ptr_mutex = ptr_mutex;
-			ptr_mutex->lock();
+		ptr_mutex_(ptr_mutex)
+#endif
+	{
+#if WITH_TBB && NO_SPINLOCK && WITH_QUEUELOCK
+#else
+		assert(ptr_mutex_ != NULL);
+		ptr_mutex_->lock();
 #endif
-		}
 	}
 
 	~ThreadSafe() {
-		if (ptr_mutex != NULL)
 #if WITH_TBB && NO_SPINLOCK && WITH_QUEUELOCK
-			delete ptr_mutex;
 #else
-			ptr_mutex->unlock();
+		ptr_mutex_->unlock();
 #endif
 	}
 
 private:
 #if WITH_TBB && NO_SPINLOCK && WITH_QUEUELOCK
-	MUTEX_T::scoped_lock* ptr_mutex;
+	MUTEX_T::scoped_lock mutex_;
 #else
-	MUTEX_T *ptr_mutex;
+	MUTEX_T *ptr_mutex_;
 #endif
 };