diff --git a/vhdlpp/expression.cc b/vhdlpp/expression.cc
index 69c0485f7..74e143c63 100644
--- a/vhdlpp/expression.cc
+++ b/vhdlpp/expression.cc
@@ -40,7 +40,7 @@ Expression::~Expression()
 
 void Expression::set_type(const VType*typ)
 {
-      assert(type_ == 0);
+      assert(type_==0 || type_==typ);
       type_ = typ;
 }
 
diff --git a/vhdlpp/expression.h b/vhdlpp/expression.h
index 233afc0fe..e5c143e3e 100644
--- a/vhdlpp/expression.h
+++ b/vhdlpp/expression.h
@@ -193,6 +193,9 @@ class ExpBinary : public Expression {
 
       void dump_operands(ostream&out, int indent = 0) const;
 
+    private:
+      virtual const VType*resolve_operand_types_(const VType*t1, const VType*t2) const;
+
     private:
       Expression*operand1_;
       Expression*operand2_;
@@ -305,6 +308,9 @@ class ExpArithmetic : public ExpBinary {
       virtual bool evaluate(ScopeBase*scope, int64_t&val) const;
       void dump(ostream&out, int indent = 0) const;
 
+    private:
+      const VType* resolve_operand_types_(const VType*t1, const VType*t2) const;
+
     private:
       fun_t fun_;
 };
diff --git a/vhdlpp/expression_elaborate.cc b/vhdlpp/expression_elaborate.cc
index f88bdbb03..2ca201d35 100644
--- a/vhdlpp/expression_elaborate.cc
+++ b/vhdlpp/expression_elaborate.cc
@@ -328,6 +328,9 @@ const VType* ExpBinary::probe_type(Entity*ent, Architecture*arc) const
       if (t1 == t2)
 	    return t1;
 
+      if (const VType*tb = resolve_operand_types_(t1, t2))
+	    return tb;
+
 	// FIXME: I should at this point try harder to find an
 	// operator that has the proper argument list and use this
 	// here, but for now we leave it for the back-end to figure out.
@@ -337,6 +340,11 @@ const VType* ExpBinary::probe_type(Entity*ent, Architecture*arc) const
       return 0;
 }
 
+const VType*ExpBinary::resolve_operand_types_(const VType*t1, const VType*t2) const
+{
+      return 0;
+}
+
 int ExpBinary::elaborate_exprs(Entity*ent, Architecture*arc, const VType*ltype)
 {
       int errors = 0;
@@ -491,6 +499,21 @@ int ExpArithmetic::elaborate_expr(Entity*ent, Architecture*arc, const VType*ltyp
       return errors;
 }
 
+const VType* ExpArithmetic::resolve_operand_types_(const VType*t1, const VType*t2) const
+{
+      while (const VTypeRange*tmp = dynamic_cast<const VTypeRange*> (t1))
+	    t1 = tmp->base_type();
+      while (const VTypeRange*tmp = dynamic_cast<const VTypeRange*> (t2))
+	    t2 = tmp->base_type();
+
+      if (t1->type_match(t2))
+	    return t1;
+      if (t2->type_match(t2))
+	    return t2;
+
+      return 0;
+}
+
 const VType* ExpAttribute::probe_type(Entity*ent, Architecture*arc) const
 {
       base_->probe_type(ent, arc);
diff --git a/vhdlpp/vtype.h b/vhdlpp/vtype.h
index 0c33b2566..e18e9ecbd 100644
--- a/vhdlpp/vtype.h
+++ b/vhdlpp/vtype.h
@@ -205,6 +205,10 @@ class VTypeRange : public VType {
       VTypeRange(const VType*base, int64_t max_val, int64_t min_val);
       ~VTypeRange();
 
+	// Get the type that is limited by the range.
+      inline const VType* base_type() const { return base_; }
+
+    public: // Virtual methods
       void write_to_stream(std::ostream&fd) const;
       int emit_def(std::ostream&out) const;