diff --git a/testing/SimHarness.cpp b/testing/SimHarness.cpp
index 8251e517..45efe633 100644
--- a/testing/SimHarness.cpp
+++ b/testing/SimHarness.cpp
@@ -66,11 +66,11 @@ void SimHarness::Release(uint8_t row, uint8_t col) {
 }
 
 void SimHarness::SetCycleTime(uint8_t millis) {
-  millis_per_cycle = millis;
+  millis_per_cycle_ = millis;
 }
 
 uint8_t SimHarness::CycleTime() const {
-  return millis_per_cycle;
+  return millis_per_cycle_;
 }
 
 
diff --git a/testing/SimHarness.h b/testing/SimHarness.h
index 76fe6edb..4256ffde 100644
--- a/testing/SimHarness.h
+++ b/testing/SimHarness.h
@@ -37,7 +37,7 @@ class SimHarness {
   void SetCycleTime(uint8_t millis);
   uint8_t CycleTime() const;
  private:
-  uint8_t millis_per_cycle = 1;
+  uint8_t millis_per_cycle_ = 1;
 };
 
 }  // namespace testing