diff --git a/PExpr.h b/PExpr.h
index e58eae287..e424355f2 100644
--- a/PExpr.h
+++ b/PExpr.h
@@ -53,7 +53,7 @@ class PExpr : public LineInfo {
 	// be. It is used by elaboration of assignments to figure out
 	// the width of the expression.
 	//
-	// The "min" is the width of the local context, so it the
+	// The "min" is the width of the local context, so is the
 	// minimum width that this function should return. Initially
 	// this is the same as the lval width.
 	//
@@ -581,6 +581,7 @@ class PEBinary : public PExpr {
 
       NetExpr*elaborate_expr_base_lshift_(Design*, NetExpr*lp, NetExpr*rp, int use_wid) const;
       NetExpr*elaborate_expr_base_rshift_(Design*, NetExpr*lp, NetExpr*rp, int use_wid) const;
+      NetExpr*elaborate_expr_base_add_(Design*, NetExpr*lp, NetExpr*rp, int use_wid) const;
 
       static void suppress_operand_sign_if_needed_(NetExpr*lp, NetExpr*rp);
 
diff --git a/netmisc.h b/netmisc.h
index cc6f9a7fe..f54237b03 100644
--- a/netmisc.h
+++ b/netmisc.h
@@ -137,9 +137,11 @@ extern unsigned count_lval_width(const class NetAssign_*first);
  * The expr_width is the width of the context where the expression is
  * being elaborated, or -1 if the expression is self-determined width.
  *
- * Also, the prune_width is the maximum width of the result, and it
- * passed to the eval_tree method of the expression to limit constant
- * results if possible.
+ * The prune_width is the maximum width of the result, and is passed
+ * to the eval_tree method of the expression to limit constant
+ * results. The evaluation will prune any constant result down to the
+ * prune_width (if >0) so should only be used at the point where it is
+ * bound to the destination.
  */
 class PExpr;
 extern NetExpr* elab_and_eval(Design*des, NetScope*scope,