diff --git a/src/common/SoundNull.hxx b/src/common/SoundNull.hxx
index afaf7179a..5e9eb24ef 100644
--- a/src/common/SoundNull.hxx
+++ b/src/common/SoundNull.hxx
@@ -48,7 +48,7 @@ class SoundNull : public Sound
     /**
       Destructor
     */
-    virtual ~SoundNull();
+    virtual ~SoundNull() { }
 
   public: 
     /**
diff --git a/src/common/SoundSDL2.cxx b/src/common/SoundSDL2.cxx
index ee5da3cee..daf9df739 100644
--- a/src/common/SoundSDL2.cxx
+++ b/src/common/SoundSDL2.cxx
@@ -482,7 +482,7 @@ void SoundSDL2::RegWriteQueue::dequeue()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-double SoundSDL2::RegWriteQueue::duration()
+double SoundSDL2::RegWriteQueue::duration() const
 {
   double duration = 0.0;
   for(uInt32 i = 0; i < mySize; ++i)
@@ -506,7 +506,7 @@ void SoundSDL2::RegWriteQueue::enqueue(const RegWrite& info)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-SoundSDL2::RegWrite& SoundSDL2::RegWriteQueue::front()
+SoundSDL2::RegWrite& SoundSDL2::RegWriteQueue::front() const
 {
   assert(mySize != 0);
   return myBuffer[myHead];
diff --git a/src/common/SoundSDL2.hxx b/src/common/SoundSDL2.hxx
index 39c3d358c..2c6be9db6 100644
--- a/src/common/SoundSDL2.hxx
+++ b/src/common/SoundSDL2.hxx
@@ -212,7 +212,7 @@ class SoundSDL2 : public Sound
         /**
           Return the duration of all the items in the queue.
         */
-        double duration();
+        double duration() const;
 
         /**
           Enqueue the specified object.
@@ -224,7 +224,7 @@ class SoundSDL2 : public Sound
 
           @return  The item at the front of the queue.
         */
-        RegWrite& front();
+        RegWrite& front() const;
 
         /**
           Answers the number of items currently in the queue.
diff --git a/src/common/StellaKeys.hxx b/src/common/StellaKeys.hxx
index 0f49bb92c..0e690567f 100644
--- a/src/common/StellaKeys.hxx
+++ b/src/common/StellaKeys.hxx
@@ -28,8 +28,9 @@
   the codebase.  The keycodes are exactly the same, but from the POV of the
   rest of the code, they are *KBD* (keyboard) keys, not *SDL* keys.
 
-  Once the codebase is ported to SDL2, the intent is to simply change this
-  file without having to modify all other classes that use StellaKey.
+  If the codebase is ported to future SDL versions or to some other toolkit,
+  the intent is to simply change this file without having to modify all
+  other classes that use StellaKey.
 
   @author  Stephen Anthony
 */
diff --git a/src/common/Version.hxx b/src/common/Version.hxx
index c0ac916af..e1fa300bb 100644
--- a/src/common/Version.hxx
+++ b/src/common/Version.hxx
@@ -22,7 +22,7 @@
 
 #include <cstdlib>
 
-#define STELLA_VERSION "4.2_beta1"
+#define STELLA_VERSION "4.2_beta2"
 #define STELLA_BUILD atoi("$Rev$" + 6)
 
 #endif
diff --git a/src/common/tv_filters/NTSCFilter.cxx b/src/common/tv_filters/NTSCFilter.cxx
index 3d8aa6f26..592789fe6 100644
--- a/src/common/tv_filters/NTSCFilter.cxx
+++ b/src/common/tv_filters/NTSCFilter.cxx
@@ -215,7 +215,7 @@ void NTSCFilter::saveConfig(Settings& settings) const
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void NTSCFilter::getAdjustables(Adjustable& adjustable, Preset preset)
+void NTSCFilter::getAdjustables(Adjustable& adjustable, Preset preset) const
 {
   switch(preset)
   {
diff --git a/src/common/tv_filters/NTSCFilter.hxx b/src/common/tv_filters/NTSCFilter.hxx
index 121f251ea..b23e8f1fe 100644
--- a/src/common/tv_filters/NTSCFilter.hxx
+++ b/src/common/tv_filters/NTSCFilter.hxx
@@ -84,7 +84,7 @@ class NTSCFilter
     // Get adjustables for the given preset
     // Values will be scaled to 0 - 100 range, independent of how
     // they're actually stored internally
-    void getAdjustables(Adjustable& adjustable, Preset preset);
+    void getAdjustables(Adjustable& adjustable, Preset preset) const;
 
     // Set custom adjustables to given values
     // Values will be scaled to 0 - 100 range, independent of how
diff --git a/src/debugger/CpuDebug.hxx b/src/debugger/CpuDebug.hxx
index 67e034a1b..441f3d25c 100644
--- a/src/debugger/CpuDebug.hxx
+++ b/src/debugger/CpuDebug.hxx
@@ -53,7 +53,7 @@ class CpuDebug : public DebuggerSystem
     string toString() { return ""; } // Not needed, since CPU stuff is always visible
 
     // I know, we ain't supposed to do this...
-    M6502& m6502() { return mySystem.m6502(); }
+    M6502& m6502() const { return mySystem.m6502(); }
 
     int pc() { return mySystem.m6502().PC; }
     int sp() { return mySystem.m6502().SP; }
diff --git a/src/debugger/Debugger.cxx b/src/debugger/Debugger.cxx
index b8c8ffe97..f3972f55d 100644
--- a/src/debugger/Debugger.cxx
+++ b/src/debugger/Debugger.cxx
@@ -430,12 +430,6 @@ bool Debugger::writeTrap(int t)
   return myWriteTraps->isSet(t) != 0;
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-int Debugger::cycles()
-{
-  return mySystem.cycles();
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void Debugger::nextScanline(int lines)
 {
diff --git a/src/debugger/Debugger.hxx b/src/debugger/Debugger.hxx
index e39a8d4a2..c908943be 100644
--- a/src/debugger/Debugger.hxx
+++ b/src/debugger/Debugger.hxx
@@ -174,7 +174,7 @@ class Debugger : public DialogContainer
     /**
       The current cycle count of the System.
     */
-    int cycles();
+    int cycles() const { return mySystem.cycles(); }
 
     string autoExec();