diff --git a/linear/GaussianFactor.cpp b/linear/GaussianFactor.cpp
index 4d6657f63..9bbfb5b09 100644
--- a/linear/GaussianFactor.cpp
+++ b/linear/GaussianFactor.cpp
@@ -227,7 +227,7 @@ list<Symbol> GaussianFactor::keys() const {
 Dimensions GaussianFactor::dimensions() const {
   Dimensions result;
   BOOST_FOREACH(const NamedMatrix& jA, As_)
-		result.insert(std::pair<Symbol,int>(jA.first,jA.second.size2()));
+		result.insert(std::pair<Symbol,size_t>(jA.first,jA.second.size2()));
   return result;
 }
 
diff --git a/linear/GaussianFactor.h b/linear/GaussianFactor.h
index b242dd368..938fcd227 100644
--- a/linear/GaussianFactor.h
+++ b/linear/GaussianFactor.h
@@ -29,7 +29,7 @@ namespace gtsam {
 	class Ordering;
 
 	/** A map from key to dimension, useful in various contexts */
-  typedef SymbolMap<int> Dimensions;
+  typedef SymbolMap<size_t> Dimensions;
 
 /**
  * Base Class for a linear factor.
diff --git a/linear/GaussianFactorGraph.cpp b/linear/GaussianFactorGraph.cpp
index 986851ff9..1cb0eb0bf 100644
--- a/linear/GaussianFactorGraph.cpp
+++ b/linear/GaussianFactorGraph.cpp
@@ -351,7 +351,7 @@ Dimensions GaussianFactorGraph::dimensions() const {
 	Dimensions result;
 	BOOST_FOREACH(const sharedFactor& factor,factors_) {
 		Dimensions vs = factor->dimensions();
-		Symbol key; int dim;
+		Symbol key; size_t dim;
 		FOREACH_PAIR(key,dim,vs) result.insert(make_pair(key,dim));
 	}
 	return result;
@@ -367,7 +367,7 @@ GaussianFactorGraph GaussianFactorGraph::add_priors(double sigma) const {
 	Dimensions vs = dimensions();
 
 	// for each of the variables, add a prior
-	Symbol key; int dim;
+	Symbol key; size_t dim;
 	FOREACH_PAIR(key,dim,vs) {
 		Matrix A = eye(dim);
 		Vector b = zero(dim);