diff --git a/wpilibc/Athena/src/PIDController.cpp b/wpilibc/Athena/src/PIDController.cpp
index ef4a49986d..c8fb63f319 100644
--- a/wpilibc/Athena/src/PIDController.cpp
+++ b/wpilibc/Athena/src/PIDController.cpp
@@ -469,6 +469,7 @@ void PIDController::SetAbsoluteTolerance(float absTolerance) {
  * @param bufLength Number of previous cycles to average. Defaults to 1.
  */
 void PIDController::SetToleranceBuffer(unsigned bufLength) {
+  std::lock_guard<priority_recursive_mutex> sync(m_mutex);
   m_bufLength = bufLength;
 
   // Cut the buffer down to size if needed.
@@ -489,10 +490,9 @@ void PIDController::SetToleranceBuffer(unsigned bufLength) {
  * This will return false until at least one input value has been computed.
  */
 bool PIDController::OnTarget() const {
+  std::lock_guard<priority_recursive_mutex> sync(m_mutex);
   if (m_buf.size() == 0) return false;
   double error = GetAvgError();
-
-  std::lock_guard<priority_recursive_mutex> sync(m_mutex);
   switch (m_toleranceType) {
     case kPercentTolerance:
       return fabs(error) < m_tolerance / 100 * (m_maximumInput - m_minimumInput);
diff --git a/wpilibc/simulation/src/PIDController.cpp b/wpilibc/simulation/src/PIDController.cpp
index f337d45b30..d3c18b5196 100644
--- a/wpilibc/simulation/src/PIDController.cpp
+++ b/wpilibc/simulation/src/PIDController.cpp
@@ -500,6 +500,7 @@ void PIDController::SetAbsoluteTolerance(float absTolerance)
  * @param bufLength Number of previous cycles to average. Defaults to 1.
  */
 void PIDController::SetToleranceBuffer(unsigned bufLength) {
+  std::lock_guard<priority_recursive_mutex> lock(m_mutex);
   m_bufLength = bufLength;
 
   // Cut the buffer down to size if needed.
@@ -518,9 +519,9 @@ void PIDController::SetToleranceBuffer(unsigned bufLength) {
  */
 bool PIDController::OnTarget() const
 {
-	double error = GetError();
-
 	std::lock_guard<priority_recursive_mutex> sync(m_mutex);
+	if (m_buf.size() == 0) return false;
+	double error = GetError();
 	switch (m_toleranceType) {
 	case kPercentTolerance:
 		return fabs(error) < m_tolerance / 100 * (m_maximumInput - m_minimumInput);