diff --git a/gtsam/inference/VariableSlots.cpp b/gtsam/inference/VariableSlots.cpp
index b1519c120..783071ae2 100644
--- a/gtsam/inference/VariableSlots.cpp
+++ b/gtsam/inference/VariableSlots.cpp
@@ -24,6 +24,8 @@ using namespace std;
 
 namespace gtsam {
 
+const size_t VariableSlots::Empty = numeric_limits<size_t>::max();
+
 /** print */
 void VariableSlots::print(const std::string& str) const {
   if(this->empty())
@@ -37,7 +39,7 @@ void VariableSlots::print(const std::string& str) const {
     for(size_t i=0; i<this->begin()->second.size(); ++i) {
       cout << "    \t";
       BOOST_FOREACH(const value_type& slot, *this) {
-        if(slot.second[i] == numeric_limits<size_t>::max())
+        if(slot.second[i] == Empty)
           cout << "x" << "\t";
         else
           cout << slot.second[i] << "\t";
diff --git a/gtsam/inference/VariableSlots.h b/gtsam/inference/VariableSlots.h
index a2ed9e5f1..d393b61b1 100644
--- a/gtsam/inference/VariableSlots.h
+++ b/gtsam/inference/VariableSlots.h
@@ -55,6 +55,7 @@ class VariableSlots : public FastMap<Key, FastVector<size_t> > {
 public:
 
   typedef FastMap<Key, FastVector<size_t> > Base;
+  static const size_t Empty;
 
   /// @name Standard Constructors
   /// @{
@@ -108,7 +109,7 @@ VariableSlots::VariableSlots(const FG& factorGraph)
       iterator thisVarSlots; bool inserted;
         boost::tie(thisVarSlots, inserted) = this->insert(std::make_pair(involvedVariable, FastVector<size_t>()));
       if(inserted)
-        thisVarSlots->second.resize(factorGraph.size(), std::numeric_limits<size_t>::max());
+        thisVarSlots->second.resize(factorGraph.size(), Empty);
       thisVarSlots->second[jointFactorPos] = factorVarSlot;
       if(debug) std::cout << "  var " << involvedVariable << " rowblock " << jointFactorPos << " comes from factor's slot " << factorVarSlot << std::endl;
       ++ factorVarSlot;
diff --git a/gtsam/linear/JacobianFactor.cpp b/gtsam/linear/JacobianFactor.cpp
index 61170129e..139f726bd 100644
--- a/gtsam/linear/JacobianFactor.cpp
+++ b/gtsam/linear/JacobianFactor.cpp
@@ -158,7 +158,7 @@ namespace gtsam {
         for(size_t sourceFactorI = 0; sourceFactorI < slots->second.size(); ++sourceFactorI)
         {
           const size_t sourceVarpos = slots->second[sourceFactorI];
-          if(sourceVarpos < numeric_limits<size_t>::max()) {
+          if(sourceVarpos != VariableSlots::Empty) {
             const JacobianFactor& sourceFactor = *factors[sourceFactorI];
             if(sourceFactor.cols() > 1) {
               foundVariable = true;
@@ -303,7 +303,7 @@ namespace gtsam {
         if(sourceRows > 0) {
           JacobianFactor::ABlock::RowsBlockXpr destBlock(destSlot.middleRows(nextRow, sourceRows));
           // Copy if exists in source factor, otherwise set zero
-          if(sourceSlot != numeric_limits<size_t>::max())
+          if(sourceSlot != VariableSlots::Empty)
             destBlock = jacobians[factorI]->getA(jacobians[factorI]->begin()+sourceSlot);
           else
             destBlock.setZero();