diff --git a/vhdlpp/expression.cc b/vhdlpp/expression.cc
index f0e7ee25b..063063772 100644
--- a/vhdlpp/expression.cc
+++ b/vhdlpp/expression.cc
@@ -20,6 +20,7 @@
  */
 
 # include  "expression.h"
+# include  "subprogram.h"
 # include  "parse_types.h"
 # include  "scope.h"
 # include  <iostream>
@@ -283,6 +284,11 @@ ExpFunc::~ExpFunc()
 	    delete argv_[idx];
 }
 
+const VType* ExpFunc::func_ret_type() const
+{
+    return def_->peek_return_type();
+}
+
 ExpInteger::ExpInteger(int64_t val)
 : value_(val)
 {
diff --git a/vhdlpp/expression.h b/vhdlpp/expression.h
index 28ab2b16f..b5b5f5c0a 100644
--- a/vhdlpp/expression.h
+++ b/vhdlpp/expression.h
@@ -477,6 +477,7 @@ class ExpFunc : public Expression {
       inline perm_string func_name() const { return name_; }
       inline size_t func_args() const { return argv_.size(); }
       inline const Expression*func_arg(size_t idx) const { return argv_[idx]; }
+      const VType*func_ret_type() const;
 
     public: // Base methods
       int elaborate_expr(Entity*ent, Architecture*arc, const VType*ltype);