diff --git a/include/llvm/CodeGen/IntrinsicLowering.h b/include/llvm/CodeGen/IntrinsicLowering.h
index 098d59c1c1d..bff1b396cd0 100644
--- a/include/llvm/CodeGen/IntrinsicLowering.h
+++ b/include/llvm/CodeGen/IntrinsicLowering.h
@@ -26,7 +26,7 @@ namespace llvm {
   class IntrinsicLowering {
     const TargetData& TD;
   public:
-    IntrinsicLowering(const TargetData &td) : TD(td) {}
+    explicit IntrinsicLowering(const TargetData &td) : TD(td) {}
 
     /// AddPrototypes - This method, if called, causes all of the prototypes
     /// that might be needed by an intrinsic lowering implementation to be
diff --git a/include/llvm/CodeGen/MachineModuleInfo.h b/include/llvm/CodeGen/MachineModuleInfo.h
index 457d33d1f26..1f9decf574c 100644
--- a/include/llvm/CodeGen/MachineModuleInfo.h
+++ b/include/llvm/CodeGen/MachineModuleInfo.h
@@ -97,7 +97,7 @@ private:
                                         // Dwarf writers.
   
 protected:
-  DebugInfoDesc(unsigned T) : Tag(T | LLVMDebugVersion) {}
+  explicit DebugInfoDesc(unsigned T) : Tag(T | LLVMDebugVersion) {}
   
 public:
   virtual ~DebugInfoDesc() {}
diff --git a/include/llvm/CodeGen/RegisterScavenging.h b/include/llvm/CodeGen/RegisterScavenging.h
index 01db6a231ed..ec23e760fa2 100644
--- a/include/llvm/CodeGen/RegisterScavenging.h
+++ b/include/llvm/CodeGen/RegisterScavenging.h
@@ -57,7 +57,7 @@ public:
     : MBB(NULL), NumPhysRegs(0), Tracking(false),
       ScavengingFrameIndex(-1), ScavengedReg(0), ScavengedRC(NULL) {};
 
-  RegScavenger(MachineBasicBlock *mbb)
+  explicit RegScavenger(MachineBasicBlock *mbb)
     : MBB(mbb), NumPhysRegs(0), Tracking(false),
       ScavengingFrameIndex(-1), ScavengedReg(0), ScavengedRC(NULL) {};
 
diff --git a/include/llvm/Support/CommandLine.h b/include/llvm/Support/CommandLine.h
index 08aca8160ac..23b7cf380e7 100644
--- a/include/llvm/Support/CommandLine.h
+++ b/include/llvm/Support/CommandLine.h
@@ -202,7 +202,7 @@ public:
   void setMiscFlag(enum MiscFlags M) { setFlag(M, M); }
   void setPosition(unsigned pos) { Position = pos; }
 protected:
-  Option(unsigned DefaultFlags)
+  explicit Option(unsigned DefaultFlags)
     : NumOccurrences(0), Flags(DefaultFlags | NormalFormatting), Position(0),
       NextRegistered(0), ArgStr(""), HelpStr(""), ValueStr("") {
     assert(getNumOccurrencesFlag() != 0 &&