diff --git a/cpp/VectorConfig.cpp b/cpp/VectorConfig.cpp
index 8577b3561..a096d271b 100644
--- a/cpp/VectorConfig.cpp
+++ b/cpp/VectorConfig.cpp
@@ -27,12 +27,11 @@ void check_size(const string& key, const Vector & vj, const Vector & dj) {
 }
 
 /* ************************************************************************* */
-VectorConfig VectorConfig::scale(double gain) {
+VectorConfig VectorConfig::scale(double gain) const {
 	VectorConfig scaled;
 	string key; Vector val;
-	FOREACH_PAIR(key, val, values) {
+	FOREACH_PAIR(key, val, values)
 		scaled.insert(key, gain*val);
-	}
 	return scaled;
 }
 
diff --git a/cpp/VectorConfig.h b/cpp/VectorConfig.h
index 32449a6be..25e327def 100644
--- a/cpp/VectorConfig.h
+++ b/cpp/VectorConfig.h
@@ -60,7 +60,7 @@ namespace gtsam {
     VectorConfig exmap(const VectorConfig & delta) const;
 
     /** Scales the configuration by a gain */
-    VectorConfig scale(double gain);
+    VectorConfig scale(double gain) const;
  
     const_iterator begin() const {return values.begin();}
     const_iterator end()   const {return values.end();}