diff --git a/cpp/base/primary_device.cpp b/cpp/base/primary_device.cpp
index ca1908ce..0ac3c1c4 100644
--- a/cpp/base/primary_device.cpp
+++ b/cpp/base/primary_device.cpp
@@ -184,7 +184,7 @@ void PrimaryDevice::Inquiry()
     DataInPhase(allocation_length);
 }
 
-void PrimaryDevice::ReportLuns()
+void PrimaryDevice::ReportLuns() const
 {
     // Only SELECT REPORT mode 0 is supported
     if (GetCdbByte(2)) {
@@ -244,7 +244,7 @@ void PrimaryDevice::RequestSense()
     DataInPhase(length);
 }
 
-void PrimaryDevice::SendDiagnostic()
+void PrimaryDevice::SendDiagnostic() const
 {
     // Do not support parameter list
     if (GetCdbByte(3) || GetCdbByte(4)) {
diff --git a/cpp/base/primary_device.h b/cpp/base/primary_device.h
index 891fb76a..b0e3ac92 100644
--- a/cpp/base/primary_device.h
+++ b/cpp/base/primary_device.h
@@ -110,7 +110,7 @@ class PrimaryDevice : public Device
 
     virtual void Inquiry();
     virtual void RequestSense();
-    void SendDiagnostic();
+    void SendDiagnostic() const;
     void ReserveUnit();
     void ReleaseUnit();
 
@@ -187,7 +187,7 @@ class PrimaryDevice : public Device
     void SetController(AbstractController*);
 
     void TestUnitReady();
-    void ReportLuns();
+    void ReportLuns() const;
 
     vector<byte> HandleRequestSense() const;
 
diff --git a/cpp/devices/tape.cpp b/cpp/devices/tape.cpp
index a2cf54a8..6492c86d 100644
--- a/cpp/devices/tape.cpp
+++ b/cpp/devices/tape.cpp
@@ -419,7 +419,7 @@ void Tape::Erase6()
     StatusPhase();
 }
 
-void Tape::ReadBlockLimits()
+void Tape::ReadBlockLimits() const
 {
     SetInt32(GetController()->GetBuffer(), 0, 0xffffff);
     SetInt16(GetController()->GetBuffer(), 4, 4);
diff --git a/cpp/devices/tape.h b/cpp/devices/tape.h
index fdb29c93..c701ee37 100644
--- a/cpp/devices/tape.h
+++ b/cpp/devices/tape.h
@@ -73,7 +73,7 @@ class Tape : public StorageDevice
     void Read6();
     void Write6();
     void Erase6();
-    void ReadBlockLimits();
+    void ReadBlockLimits() const;
     void Rewind();
     void Space6();
     void WriteFilemarks(bool);