diff --git a/src/lib/meta/function-erasure.hpp b/src/lib/meta/function-erasure.hpp
index 460143baf..f86de74b9 100644
--- a/src/lib/meta/function-erasure.hpp
+++ b/src/lib/meta/function-erasure.hpp
@@ -55,6 +55,7 @@
 
 #include "lib/util.hpp"
 #include "lib/error.hpp"
+#include "lib/bool-checkable.hpp"
 
 #include <tr1/functional>
 
@@ -76,7 +77,7 @@ namespace typelist{
    *   using the templated \c getFun()
    *   
    * @param FH policy to control the implementation.
-   *        In most cases, you should use "StoreFunction"  
+   *        In most cases, you should use "StoreFunction"
    * @note not statically typesafe. Depending on
    *       the specified policy, it \em might be
    *       run-time typesafe.
@@ -91,40 +92,19 @@ namespace typelist{
         { }
     };
   
-    
+  
   /* ====== Policy classes ====== */
-
-  template<class T>
-  struct BoolCheckable
-    {
-      typedef bool (T::*ValidityCheck)()  const;
-      typedef ValidityCheck _unspecified_bool_type;
-      
-      /** implicit conversion to "bool" */ 
-      operator _unspecified_bool_type()  const   ///< never throws
-        {
-          ValidityCheck isValid (&T::isValid);
-          T const& obj = static_cast<T const&> (*this);
-          return  (obj.*isValid)()? isValid : 0;
-        }
-      
-      bool operator! ()  const ///< never throws
-        {
-          ValidityCheck isValid (&T::isValid);
-          T const& obj = static_cast<T const&> (*this);
-          return !(obj.*isValid)();
-        }
-      
-    };
-    
+  
   /** 
    * Policy for FunErasure: store an embedded tr1::function
    * Using this policy allows to store arbitrary complex functor objects
    * embedded within a neutral container and retrieving them later type-safe.
-   * The price to pay is vtable access and heap storage of function arguments. 
+   * The price to pay is vtable access and heap storage of function arguments.
+   * 
+   * @note the bool conversion and #isValid are highly implementation dependent
    */
   class StoreFunction
-//    : public BoolCheckable<StoreFunction>
+    : public lib::BoolCheckable<StoreFunction>
     {
       /** Helper: type erasure */
       struct Holder
@@ -181,7 +161,7 @@ namespace typelist{
         }
       
       bool
-      isValid()  const
+      isValid()  const   ///< @note implementation dependent!!
         {
           return reinterpret_cast<void*> (holder_.storage_[0]);
         }
@@ -195,6 +175,7 @@ namespace typelist{
    * The price to pay is vtable access. 
    */
   class StoreFunPtr
+    : public lib::BoolCheckable<StoreFunPtr>
     {
       /** Helper: type erasure */
       struct Holder
@@ -241,6 +222,13 @@ namespace typelist{
           REQUIRE (INSTANCEOF (FunctionHolder<SIG>, &holder_));
           return static_cast<FunctionHolder<SIG>&> (holder_).get();
         }
+      
+      
+      bool
+      isValid()  const
+        {
+          return holder_.fP_;
+        }
     };
   
   
@@ -250,6 +238,7 @@ namespace typelist{
    * and to retrieve it without overhead, but also without safety.
    */
   class StoreUncheckedFunPtr
+    : public lib::BoolCheckable<StoreUncheckedFunPtr>
     {
       void *funP_;
       
@@ -271,6 +260,13 @@ namespace typelist{
         {
           return *reinterpret_cast<SIG*> (funP_);
         }
+      
+      
+      bool
+      isValid()  const
+        {
+          return funP_;
+        }
     };
   
   
diff --git a/src/proc/control/command-mutation.hpp b/src/proc/control/command-mutation.hpp
index df32cfe22..f0f77d704 100644
--- a/src/proc/control/command-mutation.hpp
+++ b/src/proc/control/command-mutation.hpp
@@ -84,7 +84,7 @@ namespace control {
       close (CmdClosure& cmdClosure)
         {
           REQUIRE (!clo_, "Lifecycle error: already closed over the arguments");
-//          REQUIRE (func_, "Param error: not bound to a valid function");
+          REQUIRE (func_, "Param error: not bound to a valid function");
           func_ = cmdClosure.bindArguments(func_);
           clo_ = &cmdClosure;
           return *this;
@@ -117,7 +117,7 @@ namespace control {
       virtual bool
       isValid ()   const
         {
-//          return func_ && clo_;
+          return func_ && clo_;
         }
       
       void
@@ -177,7 +177,7 @@ namespace control {
       close (CmdClosure& cmdClosure)
         {
           REQUIRE (!memento_,    "Lifecycle error: already closed over the arguments");
-//          REQUIRE (captureFunc_, "Param error: not bound to a valid function");
+          REQUIRE (captureFunc_, "Param error: not bound to a valid function");
           
           // create a special state closure, which can later on store the captured undo state (memento)
           scoped_ptr<CmdClosure> stateClosure (new MementoClosure (captureFunc_));
@@ -213,7 +213,7 @@ namespace control {
       virtual bool
       isValid ()   const
         {
-//          return Mutation::isValid() && captureFunc_ && memento_;
+          return Mutation::isValid() && captureFunc_ && memento_;
         }
       
       
diff --git a/tests/lib/meta/function-erasure-test.cpp b/tests/lib/meta/function-erasure-test.cpp
index 6d98582f1..43320c453 100644
--- a/tests/lib/meta/function-erasure-test.cpp
+++ b/tests/lib/meta/function-erasure-test.cpp
@@ -212,10 +212,10 @@ namespace test {
           
           typedef typename BuildEmptyHolder<HOL>::Type EmptyHolder;
           EmptyHolder emptyHolder;
-//          ASSERT (!emptyHolder);
-//          ASSERT ( h1 );
-//          ASSERT ( h2 );
-//          ASSERT ( h3 );
+          ASSERT (!emptyHolder);
+          ASSERT ( h1 );
+          ASSERT ( h2 );
+          ASSERT ( h3 );
         }