diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index a62ebad..0d0b746 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/lib/AST/DeclCXX.cpp
@@ -61,6 +61,12 @@
 }
 
 QualType CXXMethodDecl::getThisType(ASTContext &C) const {
+  // C++ 9.3.2p1: The type of this in a member function of a class X is X*.
+  // If the member function is declared const, the type of this is const X*,
+  // if the member function is declared volatile, the type of this is
+  // volatile X*, and if the member function is declared const volatile,
+  // the type of this is const volatile X*.
+
   assert(isInstance() && "No 'this' for static methods!");
   QualType ClassTy = C.getTagDeclType(const_cast<CXXRecordDecl*>(
                                             cast<CXXRecordDecl>(getParent())));