diff --git a/vhdlpp/vtype.h b/vhdlpp/vtype.h
index 800c0bbd3..3b9356e60 100644
--- a/vhdlpp/vtype.h
+++ b/vhdlpp/vtype.h
@@ -168,6 +168,7 @@ class VTypePrimitive : public VType {
 
       VType*clone() const { return new VTypePrimitive(*this); }
 
+      bool type_match(const VType*that) const;
       void write_to_stream(std::ostream&fd) const;
       void show(std::ostream&) const;
       int get_width(ScopeBase*scope) const;
@@ -221,6 +222,7 @@ class VTypeArray : public VType {
       VType*clone() const;
 
       int elaborate(Entity*ent, ScopeBase*scope) const;
+      bool type_match(const VType*that) const;
       void write_to_stream(std::ostream&fd) const;
       void write_type_to_stream(std::ostream&fd) const;
       void show(std::ostream&) const;
diff --git a/vhdlpp/vtype_match.cc b/vhdlpp/vtype_match.cc
index 86c8f90ff..459217879 100644
--- a/vhdlpp/vtype_match.cc
+++ b/vhdlpp/vtype_match.cc
@@ -38,5 +38,43 @@ bool VTypeDef::type_match(const VType*that) const
       if(VType::type_match(that))
           return true;
 
-      return VType::type_match(type_);
+      return type_->type_match(that);
+}
+
+bool VTypePrimitive::type_match(const VType*that) const
+{
+      if(VType::type_match(that))
+          return true;
+
+      if(const VTypePrimitive*prim = dynamic_cast<const VTypePrimitive*>(that)) {
+          // TODO it is not always true, but works for many cases
+          type_t that_type = prim->type();
+          return ((type_ == NATURAL || type_ == INTEGER) &&
+              (that_type == NATURAL || that_type == INTEGER));
+      }
+
+      return false;
+}
+
+bool VTypeArray::type_match(const VType*that) const
+{
+      if(VType::type_match(that))
+          return true;
+
+      // Check if both arrays are of the same size
+      if(const VTypeArray*arr = dynamic_cast<const VTypeArray*>(that)) {
+          if(!element_type()->type_match(arr->element_type()))
+              return false;
+
+          int this_width = get_width(NULL);
+          int that_width = arr->get_width(NULL);
+
+          // Either one of the sizes is undefined, or both are the same size
+          if(this_width > 0 && that_width > 0 && this_width != that_width)
+              return false;
+
+          return true;
+      }
+
+      return false;
 }