diff --git a/elab_scope.cc b/elab_scope.cc
index 37f186e93..36cf94a96 100644
--- a/elab_scope.cc
+++ b/elab_scope.cc
@@ -475,7 +475,12 @@ bool PGenerate::generate_scope_loop_(Design*des, NetScope*container)
       container->genvar_tmp_val = genvar;
       NetExpr*test_ex = elab_and_eval(des, container, loop_test, -1);
       NetEConst*test = dynamic_cast<NetEConst*>(test_ex);
-      assert(test);
+      if (test == 0) {
+	    cerr << get_fileline() << ": error: Cannot evaluate genvar"
+		 << " conditional expression: " << *loop_test << endl;
+	    des->errors += 1;
+	    return false;
+      }
       while (test->value().as_long()) {
 
 	      // The actual name of the scope includes the genvar so
@@ -522,7 +527,12 @@ bool PGenerate::generate_scope_loop_(Design*des, NetScope*container)
 	      // Calculate the step for the loop variable.
 	    NetExpr*step_ex = elab_and_eval(des, container, loop_step, -1);
 	    NetEConst*step = dynamic_cast<NetEConst*>(step_ex);
-	    assert(step);
+	    if (step == 0) {
+		  cerr << get_fileline() << ": error: Cannot evaluate genvar"
+		       << " step expression: " << *loop_step << endl;
+		  des->errors += 1;
+		  return false;
+	    }
 	    if (debug_scopes)
 		  cerr << get_fileline() << ": debug: genvar step from "
 		       << genvar << " to " << step->value().as_long() << endl;
@@ -547,7 +557,12 @@ bool PGenerate::generate_scope_condit_(Design*des, NetScope*container, bool else
 {
       NetExpr*test_ex = elab_and_eval(des, container, loop_test, -1);
       NetEConst*test = dynamic_cast<NetEConst*> (test_ex);
-      assert(test);
+      if (test == 0) {
+	    cerr << get_fileline() << ": error: Cannot evaluate genvar"
+		 << " conditional expression: " << *loop_test << endl;
+	    des->errors += 1;
+	    return false;
+      }
 
 	// If the condition evaluates as false, then do not create the
 	// scope.
@@ -589,7 +604,12 @@ bool PGenerate::generate_scope_case_(Design*des, NetScope*container)
 {
       NetExpr*case_value_ex = elab_and_eval(des, container, loop_test, -1);
       NetEConst*case_value_co = dynamic_cast<NetEConst*>(case_value_ex);
-      assert(case_value_co);
+      if (case_value_co == 0) {
+	    cerr << get_fileline() << ": error: Cannot evaluate genvar case"
+		 << " expression: " << *loop_test << endl;
+	    des->errors += 1;
+	    return false;
+      }
 
 	// The name of the scope to generate, whatever that item is.
       hname_t use_name (scope_name);