diff --git a/Module.h b/Module.h
index 5985ab717..3222a2838 100644
--- a/Module.h
+++ b/Module.h
@@ -121,7 +121,7 @@ class Module : public PScope, public LineInfo {
 
 	/* The module has a list of genvars that may be used in
 	   various generate schemes. */
-      list<pair<perm_string,LineInfo*> > genvars;
+      map<perm_string,LineInfo*> genvars;
 
 	/* the module has a list of generate schemes that appear in
 	   the module definition. These are used at elaboration time. */
diff --git a/PExpr.cc b/PExpr.cc
index aa1265856..96428204f 100644
--- a/PExpr.cc
+++ b/PExpr.cc
@@ -191,7 +191,7 @@ PEIdent::~PEIdent()
 
 /*
  * An identifier can be in a constant expression if (and only if) it is
- * a parameter.
+ * a parameter or genvar.
  *
  * NOTE: This test does not work if the name is hierarchical!
  */
@@ -212,6 +212,11 @@ bool PEIdent::is_constant(Module*mod) const
 	if (cur != mod->localparams.end()) return true;
       }
 
+      { map<perm_string,LineInfo*>::const_iterator cur;
+        cur = mod->genvars.find(tmp);
+	if (cur != mod->genvars.end()) return true;
+      }
+
       return false;
 }
 
diff --git a/pform.cc b/pform.cc
index 8a613fb13..295262eed 100644
--- a/pform.cc
+++ b/pform.cc
@@ -369,8 +369,7 @@ void pform_genvars(const struct vlltype&li, list<perm_string>*names)
       for (cur = names->begin(); cur != names->end() ; *cur++) {
 	    LineInfo*lni = new LineInfo();
 	    FILE_NAME(lni, li);
-	    pform_cur_module->genvars.push_back(
-	          pair<perm_string,LineInfo*>(*cur, lni));
+	    pform_cur_module->genvars[*cur] = lni;
       }
 
       delete names;
diff --git a/pform_dump.cc b/pform_dump.cc
index 9bcc7efa3..1473865ee 100644
--- a/pform_dump.cc
+++ b/pform_dump.cc
@@ -995,7 +995,7 @@ void Module::dump(ostream&out) const
 		  out << "/* ERROR */;" << endl;
       }
 
-      typedef list<pair<perm_string,LineInfo*> >::const_iterator genvar_iter_t;
+      typedef map<perm_string,LineInfo*>::const_iterator genvar_iter_t;
       for (genvar_iter_t cur = genvars.begin()
 		 ; cur != genvars.end() ; cur++) {
 	    out << "    genvar " << ((*cur).first) << ";" << endl;