diff --git a/Storage/Disk/DiskDrive.cpp b/Storage/Disk/DiskDrive.cpp
index 12c2d5c55..3492a5bcb 100644
--- a/Storage/Disk/DiskDrive.cpp
+++ b/Storage/Disk/DiskDrive.cpp
@@ -13,7 +13,6 @@ using namespace Storage;
 DiskDrive::DiskDrive(unsigned int clock_rate, unsigned int clock_rate_multiplier, unsigned int revolutions_per_minute) :
 	_clock_rate(clock_rate * clock_rate_multiplier),
 	_clock_rate_multiplier(clock_rate_multiplier),
-	_revolutions_per_minute(revolutions_per_minute),
 	_head_position(0),
 
 	TimedEventLoop(clock_rate * clock_rate_multiplier)
diff --git a/Storage/Disk/DiskDrive.hpp b/Storage/Disk/DiskDrive.hpp
index ee7674d0b..216a1626b 100644
--- a/Storage/Disk/DiskDrive.hpp
+++ b/Storage/Disk/DiskDrive.hpp
@@ -92,7 +92,6 @@ class DiskDrive: public DigitalPhaseLockedLoop::Delegate, public TimedEventLoop
 		Time _bit_length;
 		unsigned int _clock_rate;
 		unsigned int _clock_rate_multiplier;
-		unsigned int _revolutions_per_minute;
 		Time _rotational_multiplier;
 
 		std::shared_ptr<DigitalPhaseLockedLoop> _pll;