diff --git a/src/dolo/symbolic/ramsey.py b/src/dolo/symbolic/ramsey.py
index <HASH>..<HASH> 100644
--- a/src/dolo/symbolic/ramsey.py
+++ b/src/dolo/symbolic/ramsey.py
@@ -27,6 +27,7 @@ class RamseyModel(Model):
         context = dict()
         for v in self.variables_ordering + self.parameters_ordering + self.shocks_ordering:
             context[v.name] = v
+        context['exp'] = sympy.exp
         return sympy.sympify( eval(string,context) )
 
     def build_lagrangian(self):
@@ -56,4 +57,4 @@ def time_shift(expr,n):
             return e(n)
         else:
             return e
-    return map_function_to_expression(f,expr)
\ No newline at end of file
+    return map_function_to_expression(f,expr)
quickfix : added exp to names understood in ramsey objective