diff --git a/syn-rules.y b/syn-rules.y
index 1507b08df..8a86fe6e5 100644
--- a/syn-rules.y
+++ b/syn-rules.y
@@ -1,7 +1,7 @@
 
 %{
 /*
- * Copyright (c) 2000-2010 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2014 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
@@ -100,7 +100,13 @@ static void hookup_DFF_CE(NetFF*ff, NetESignal*d, NetEvProbe*pclk,
                           NetNet*ce, NetAssign_*a, unsigned rval_pinoffset)
 {
 
-      assert(rval_pinoffset == 0);
+      if (rval_pinoffset != 0) {
+	    cerr << a->get_fileline() << ": sorry: "
+                 << "unable to hook up an R-value with offset "
+	         << rval_pinoffset << " to signal " << a->name()
+	         << "." << endl;
+	    return;
+      }
 	// a->sig() is a *NetNet, which doesn't have the loff_ and
 	// lwid_ context.  Add the correction for loff_ ourselves.
 
diff --git a/synth2.cc b/synth2.cc
index d2e54e797..dcc80895d 100644
--- a/synth2.cc
+++ b/synth2.cc
@@ -82,7 +82,15 @@ bool NetAssignBase::synth_async(Design*des, NetScope*scope,
 	    des->errors += 1;
 	    return false;
       }
-      assert(lval_->more == 0);
+      if (lval_->more) {
+	    cerr << get_fileline() << ": sorry: "
+		 << "NetAssignBase::synth_async does not support an "
+	         << "L-value concatenation ";
+	    dump_lval(cerr);
+	    cerr << endl;
+	    des->errors += 1;
+	    return false;
+      }
 
       if (debug_synth2) {
 	    cerr << get_fileline() << ": NetAssignBase::synth_async: "
@@ -1308,7 +1316,7 @@ bool NetCondit::synth_sync(Design*des, NetScope*scope,
 	    NetBus tmp_out(scope, nex_out.pin_count());
 	    NetBus accumulated_tmp_out(scope, nex_out.pin_count());
 	    flag = if_->synth_async(des, scope, nex_map, tmp_out, accumulated_tmp_out);
-	    ivl_assert(*this, flag);
+	    if (! flag) return false;
 
 	    ivl_assert(*this, tmp_out.pin_count() == ff_aclr.pin_count());
 	    ivl_assert(*this, tmp_out.pin_count() == ff_aset.pin_count());
diff --git a/vhdlpp/expression.cc b/vhdlpp/expression.cc
index 526d06be2..feeddd88e 100644
--- a/vhdlpp/expression.cc
+++ b/vhdlpp/expression.cc
@@ -307,12 +307,6 @@ ExpReal::~ExpReal()
 {
 }
 
-bool ExpReal::evaluate(ScopeBase*, double&val) const
-{
-      val = value_;
-      return true;
-}
-
 ExpLogical::ExpLogical(ExpLogical::fun_t ty, Expression*op1, Expression*op2)
 : ExpBinary(op1, op2), fun_(ty)
 {
diff --git a/vhdlpp/expression.h b/vhdlpp/expression.h
index d26a8c5df..7b54705c6 100644
--- a/vhdlpp/expression.h
+++ b/vhdlpp/expression.h
@@ -519,7 +519,6 @@ class ExpReal : public Expression {
       int emit(ostream&out, Entity*ent, Architecture*arc);
       int emit_package(std::ostream&out);
       bool is_primary(void) const;
-      bool evaluate(ScopeBase*scope, double&val) const;
       void dump(ostream&out, int indent = 0) const;
       virtual ostream& dump_inline(ostream&out) const;