diff --git a/design_dump.cc b/design_dump.cc
index 9fa0ba876..f6540a6da 100644
--- a/design_dump.cc
+++ b/design_dump.cc
@@ -1124,7 +1124,10 @@ void NetAssign::dump(ostream&o, unsigned ind) const
       if (const NetExpr*de = get_delay())
 	    o << "#(" << *de << ") ";
 
-      o << *rval() << ";" << endl;
+      if (rval())
+	    o << *rval() << ";" << endl;
+      else
+	    o << "<rval elaboration error>;" << endl;
 }
 
 void NetAssignNB::dump(ostream&o, unsigned ind) const
@@ -1142,7 +1145,10 @@ void NetAssignNB::dump(ostream&o, unsigned ind) const
 	    o << *event_;
       }
 
-      o << *rval() << ";" << endl;
+      if (rval())
+	    o << *rval() << ";" << endl;
+      else
+	    o << "rval elaboration error>;" << endl;
 
 }
 
diff --git a/net_func_eval.cc b/net_func_eval.cc
index 136be7805..58b7d629d 100644
--- a/net_func_eval.cc
+++ b/net_func_eval.cc
@@ -441,8 +441,11 @@ bool NetAssign::eval_func_lval_(const LineInfo&loc,
 bool NetAssign::evaluate_function(const LineInfo&loc,
 				  map<perm_string,LocalVar>&context_map) const
 {
-	// Evaluate the r-value expression.
-      NetExpr*rval_result = rval()->evaluate_function(loc, context_map);
+      // Evaluate the r-value expression.
+      const NetExpr*use_rval = rval();
+      if (use_rval == 0)
+	    return false;
+      NetExpr*rval_result = use_rval->evaluate_function(loc, context_map);
       if (rval_result == 0)
 	    return false;