diff --git a/elab_expr.cc b/elab_expr.cc
index 115d17c61..a018593d4 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -1682,18 +1682,20 @@ NetExpr* PEConcat::elaborate_expr(Design*des, NetScope*scope,
 
 	    ex->set_line(*parms_[idx]);
 
+	    if (ex->expr_type() == IVL_VT_REAL) {
+		  cerr << ex->get_fileline() << ": error: "
+		       << "concatenation operand can not be real: "
+		       << *parms_[idx] << endl;
+		  des->errors += 1;
+		  continue;
+	    }
+
 	    if (! ex->has_width()) {
 		  cerr << ex->get_fileline() << ": error: "
 		       << "concatenation operand has indefinite width: "
 		       << *ex << endl;
 		  des->errors += 1;
-	    }
-
-	    if (ex->expr_type() == IVL_VT_REAL) {
-		  cerr << ex->get_fileline() << ": error: "
-		       << "concatenation operand can not be REAL: "
-		       << *ex << endl;
-		  des->errors += 1;
+		  continue;
 	    }
 
 	    wid_sum += ex->expr_width();
@@ -1707,6 +1709,7 @@ NetExpr* PEConcat::elaborate_expr(Design*des, NetScope*scope,
 	         << "have zero width in this context." << endl;
 	    des->errors += 1;
 	    concat_depth -= 1;
+	    delete tmp;
 	    return 0;
       }
 
diff --git a/elab_lval.cc b/elab_lval.cc
index 3db84356f..63f0c40c2 100644
--- a/elab_lval.cc
+++ b/elab_lval.cc
@@ -118,17 +118,20 @@ NetAssign_* PEConcat::elaborate_lval(Design*des,
 
 	    NetAssign_*tmp = parms_[idx]->elaborate_lval(des, scope, is_force);
 
+	    if (tmp->expr_type() == IVL_VT_REAL) {
+		  cerr << parms_[idx]->get_fileline() << ": error: "
+		       << "concatenation operand can not be real: "
+		       << *parms_[idx] << endl;
+		  des->errors += 1;
+		  continue;
+	    }
+
 	      /* If the l-value doesn't elaborate, the error was
 		 already detected and printed. We just skip it and let
 		 the compiler catch more errors. */
-	    if (tmp == 0)
-		  continue;
-
-	    assert(tmp);
-
+	    if (tmp == 0) continue;
 
 	      /* Link the new l-value to the previous one. */
-
 	    NetAssign_*last = tmp;
 	    while (last->more)
 		  last = last->more;
diff --git a/elab_net.cc b/elab_net.cc
index 6ef1aaa0d..40cbc7383 100644
--- a/elab_net.cc
+++ b/elab_net.cc
@@ -72,10 +72,16 @@ NetNet* PEConcat::elaborate_lnet_common_(Design*des, NetScope*scope,
 	    } else {
 		  nets[idx] = parms_[idx]->elaborate_lnet(des, scope);
 	    }
-	    if (nets[idx] == 0)
+
+	    if (nets[idx] == 0) errors += 1;
+	    else if (nets[idx]->data_type() == IVL_VT_REAL) {
+		  cerr << parms_[idx]->get_fileline() << ": error: "
+		       << "concatenation operand can no be real: "
+		       << *parms_[idx] << endl;
 		  errors += 1;
-	    else
-		  width += nets[idx]->vector_width();
+		  continue;
+	    } else width += nets[idx]->vector_width();
+
       }
 
 	/* If any of the sub expressions failed to elaborate, then
diff --git a/elab_pexpr.cc b/elab_pexpr.cc
index fb1454dca..b7e243341 100644
--- a/elab_pexpr.cc
+++ b/elab_pexpr.cc
@@ -150,11 +150,19 @@ NetEConcat* PEConcat::elaborate_pexpr(Design*des, NetScope*scope) const
 	/* Elaborate all the operands and attach them to the concat
 	   node. Use the elaborate_pexpr method instead of the
 	   elaborate_expr method. */
+      bool fail = false;
       for (unsigned idx = 0 ;  idx < parms_.count() ;  idx += 1) {
 	    assert(parms_[idx]);
 	    NetExpr*ex = parms_[idx]->elaborate_pexpr(des, scope);
 	    if (ex == 0) continue;
 
+	    if (ex->expr_type() == IVL_VT_REAL) {
+		  cerr << ex->get_fileline() << ": error: concatenation "
+		       << "operand can not be real: " << *ex << endl;
+		  des->errors += 1;
+		  fail = true;
+		  continue;
+	    }
 	    ex->set_line(*parms_[idx]);
 
 	    if (dynamic_cast<NetEParam*>(ex)) {
@@ -167,13 +175,18 @@ NetEConcat* PEConcat::elaborate_pexpr(Design*des, NetScope*scope) const
 		       << "concatenation has indefinite width: "
 		       << *ex << endl;
 		  des->errors += 1;
-		  delete tmp;
-		  return 0;
+		  fail = true;
+		  continue;
 	    }
 
 	    tmp->set(idx, ex);
       }
 
+      if (fail) {
+	    delete tmp;
+	    return 0;
+      }
+
       return tmp;
 }
 
diff --git a/net_design.cc b/net_design.cc
index 7f3ad88f1..0e09642e4 100644
--- a/net_design.cc
+++ b/net_design.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2007 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2009 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -490,7 +490,7 @@ void NetScope::evaluate_parameter_logic_(Design*des, param_ref_t cur)
 void NetScope::evaluate_parameter_real_(Design*des, param_ref_t cur)
 {
       NetExpr*expr = (*cur).second.expr;
-      assert(expr);
+      if (expr == NULL) return;  // This is an invalid parameter so return.
 
       NetECReal*res = 0;
       eval_expr(expr);