diff --git a/elab_pexpr.cc b/elab_pexpr.cc
index b27319d64..961588083 100644
--- a/elab_pexpr.cc
+++ b/elab_pexpr.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: elab_pexpr.cc,v 1.9 2001/07/25 03:10:49 steve Exp $"
+#ident "$Id: elab_pexpr.cc,v 1.10 2001/10/07 03:38:08 steve Exp $"
 #endif
 
 # include "config.h"
@@ -101,7 +101,22 @@ NetEConcat* PEConcat::elaborate_pexpr(Design*des, NetScope*scope) const
 	    assert(parms_[idx]);
 	    NetExpr*ex = parms_[idx]->elaborate_pexpr(des, scope);
 	    if (ex == 0) continue;
+
 	    ex->set_line(*parms_[idx]);
+
+	    if (! ex->has_width()) {
+		  cerr << ex->get_line() << ": error: operand of "
+		       << "concatenation has indefinite width: "
+		       << *ex << endl;
+		  des->errors += 1;
+
+	    } else if (ex->expr_width() == 0) {
+		  cerr << ex->get_line() << ": internal error: "
+		       << "Operand of concatenation has no width: "
+		       << *ex << endl;
+		  des->errors += 1;
+	    }
+
 	    tmp->set(idx, ex);
       }
 
@@ -203,6 +218,9 @@ NetExpr*PEUnary::elaborate_pexpr (Design*des, NetScope*scope) const
 
 /*
  * $Log: elab_pexpr.cc,v $
+ * Revision 1.10  2001/10/07 03:38:08  steve
+ *  parameter names do not have defined size.
+ *
  * Revision 1.9  2001/07/25 03:10:49  steve
  *  Create a config.h.in file to hold all the config
  *  junk, and support gcc 3.0. (Stephan Boettcher)
diff --git a/netlist.cc b/netlist.cc
index 0799b06ee..fb4da5007 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: netlist.cc,v 1.171 2001/09/29 01:53:22 steve Exp $"
+#ident "$Id: netlist.cc,v 1.172 2001/10/07 03:38:08 steve Exp $"
 #endif
 
 # include "config.h"
@@ -2144,6 +2144,11 @@ NetEParam::~NetEParam()
 {
 }
 
+bool NetEParam::has_width() const
+{
+      return false;
+}
+
 NetEParam* NetEParam::dup_expr() const
 {
       return new NetEParam(des_, scope_, name_);
@@ -2424,6 +2429,9 @@ const NetProc*NetTaskDef::proc() const
 
 /*
  * $Log: netlist.cc,v $
+ * Revision 1.172  2001/10/07 03:38:08  steve
+ *  parameter names do not have defined size.
+ *
  * Revision 1.171  2001/09/29 01:53:22  steve
  *  Fix the size of unsized constant operants to compare (PR#274)
  *
diff --git a/netlist.h b/netlist.h
index 9f20ebe88..dbac47b95 100644
--- a/netlist.h
+++ b/netlist.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: netlist.h,v 1.214 2001/08/25 23:50:03 steve Exp $"
+#ident "$Id: netlist.h,v 1.215 2001/10/07 03:38:08 steve Exp $"
 #endif
 
 /*
@@ -2279,6 +2279,7 @@ class NetEParam  : public NetExpr {
       ~NetEParam();
 
       virtual bool set_width(unsigned w);
+      virtual bool has_width() const;
       virtual void expr_scan(struct expr_scan_t*) const;
       virtual NetExpr* eval_tree();
       virtual NetEParam* dup_expr() const;
@@ -2847,6 +2848,9 @@ extern ostream& operator << (ostream&, NetNet::Type);
 
 /*
  * $Log: netlist.h,v $
+ * Revision 1.215  2001/10/07 03:38:08  steve
+ *  parameter names do not have defined size.
+ *
  * Revision 1.214  2001/08/25 23:50:03  steve
  *  Change the NetAssign_ class to refer to the signal
  *  instead of link into the netlist. This is faster