diff --git a/include/llvm/SymbolTable.h b/include/llvm/SymbolTable.h
index 85023755810..22a9acd438c 100644
--- a/include/llvm/SymbolTable.h
+++ b/include/llvm/SymbolTable.h
@@ -42,7 +42,7 @@ public:
   ~SymbolTable();
 
   // lookup - Returns null on failure...
-  Value *lookup(const Type *Ty, const std::string &name);
+  Value *lookup(const Type *Ty, const std::string &name) const;
 
   // insert - Add named definition to the symbol table...
   inline void insert(Value *N) {
diff --git a/lib/VMCore/SymbolTable.cpp b/lib/VMCore/SymbolTable.cpp
index 8c9e86c0030..be1459e70b7 100644
--- a/lib/VMCore/SymbolTable.cpp
+++ b/lib/VMCore/SymbolTable.cpp
@@ -72,10 +72,10 @@ std::string SymbolTable::getUniqueName(const Type *Ty,
 
 
 // lookup - Returns null on failure...
-Value *SymbolTable::lookup(const Type *Ty, const std::string &Name) {
-  iterator I = find(Ty);
+Value *SymbolTable::lookup(const Type *Ty, const std::string &Name) const {
+  const_iterator I = find(Ty);
   if (I != end()) {                      // We have symbols in that plane...
-    type_iterator J = I->second.find(Name);
+    type_const_iterator J = I->second.find(Name);
     if (J != I->second.end())            // and the name is in our hash table...
       return J->second;
   }