diff --git a/tgt-vhdl/expr.cc b/tgt-vhdl/expr.cc
index 6eb4b42ca..0b928d4cb 100644
--- a/tgt-vhdl/expr.cc
+++ b/tgt-vhdl/expr.cc
@@ -533,7 +533,6 @@ static vhdl_expr *translate_ufunc(ivl_expr_t e)
    vhdl_fcall *fcall = new vhdl_fcall(funcname, rettype);
 
    int nparams = ivl_expr_parms(e);
-   int func_scope_sig = 0;
    for (int i = 0; i < nparams; i++) {
       vhdl_expr *param = translate_expr(ivl_expr_parm(e, i));
       if (NULL == param) {
@@ -542,10 +541,8 @@ static vhdl_expr *translate_ufunc(ivl_expr_t e)
       }
       
       // Ensure the parameter has the correct VHDL type
-      ivl_signal_t param_sig;
-      do {
-          param_sig = ivl_scope_sig(defscope, func_scope_sig++);
-      } while (ivl_signal_port(param_sig) != IVL_SIP_INPUT);
+      // Parameter number is i + 1 since 0th parameter is return value
+      ivl_signal_t param_sig = ivl_scope_port(defscope, i + 1);
       vhdl_type *param_type =
          vhdl_type::type_for(ivl_signal_width(param_sig),
                              ivl_signal_signed(param_sig) != 0);