diff --git a/hphp/runtime/vm/unit-inl.h b/hphp/runtime/vm/unit-inl.h
index a678af3..5ce8ef6 100644
--- a/hphp/runtime/vm/unit-inl.h
+++ b/hphp/runtime/vm/unit-inl.h
@@ -48,20 +48,24 @@ inline void SourceLoc::setLoc(const Location* l) {
 inline bool SourceLoc::same(const SourceLoc* l) const {
   return (this == l) ||
          (line0 == l->line0 && char0 == l->char0 &&
           line1 == l->line1 && char1 == l->char1);
 }

 inline bool SourceLoc::operator==(const SourceLoc& l) const {
   return same(&l);
 }

+inline bool SourceLoc::operator!=(const SourceLoc& l) const {
+  return !same(&l);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Location tables.

 template<typename T>
 Offset TableEntry<T>::pastOffset() const {
   return m_pastOffset;
 }

 template<typename T>
 T TableEntry<T>::val() const {
diff --git a/hphp/runtime/vm/unit.cpp b/hphp/runtime/vm/unit.cpp
index 3a4edb5..51206c9 100644
--- a/hphp/runtime/vm/unit.cpp
+++ b/hphp/runtime/vm/unit.cpp
@@ -599,21 +599,21 @@ Class* Unit::defClass(const PreClass* preClass,
   if (auto current = nameList->getCachedTypeAlias()) {
     FrameRestore fr(preClass);
     raise_error("Cannot declare class with the same name (%s) as an "
                 "existing type", current->name->data());
     return nullptr;
   }

   // If there was already a class declared with DefClass, check if
   // it's compatible.
   if (Class* cls = nameList->getCachedClass()) {
-    if (cls->preClass() != preClass) {
+    if (cls->preClass() != preClass) { // This?
       if (failIsFatal) {
         FrameRestore fr(preClass);
         raise_error("Class already declared: %s", preClass->name()->data());
       }
       return nullptr;
     }
     return cls;
   }

   // Get a compatible Class, and add it to the list of defined classes.
diff --git a/hphp/runtime/vm/unit.h b/hphp/runtime/vm/unit.h
index 0b86083..61eab83 100644
--- a/hphp/runtime/vm/unit.h
+++ b/hphp/runtime/vm/unit.h
@@ -84,20 +84,21 @@ struct SourceLoc {
   /*
    * Set to a parser Location.
    */
   void setLoc(const Location* l);

   /*
    * Equality.
    */
   bool same(const SourceLoc* l) const;
   bool operator==(const SourceLoc& l) const;
+  bool operator!=(const SourceLoc& l) const;

   /*
    * Start and end lines and characters.
    *
    * The default {1, 1, 1, 1} is an invalid sentinel value.
    */
   int line0{1};
   int char0{1};
   int line1{1};
   int char1{1};