diff --git a/tools/widl/header.c b/tools/widl/header.c
index 6cf52b17f41..6e4a8fca09f 100644
--- a/tools/widl/header.c
+++ b/tools/widl/header.c
@@ -363,7 +363,7 @@ void write_expr(FILE *h, const expr_t *e, int brackets)
   case EXPR_VOID:
     break;
   case EXPR_NUM:
-    fprintf(h, "%ld", e->u.lval);
+    fprintf(h, "%lu", e->u.lval);
     break;
   case EXPR_HEXNUM:
     fprintf(h, "0x%lx", e->u.lval);
diff --git a/tools/widl/typegen.c b/tools/widl/typegen.c
index b72e87b30fc..9d13a2d9abd 100644
--- a/tools/widl/typegen.c
+++ b/tools/widl/typegen.c
@@ -2177,7 +2177,7 @@ static void write_struct_expr(FILE *h, const expr_t *e, int brackets,
         case EXPR_VOID:
             break;
         case EXPR_NUM:
-            fprintf(h, "%ld", e->u.lval);
+            fprintf(h, "%lu", e->u.lval);
             break;
         case EXPR_HEXNUM:
             fprintf(h, "0x%lx", e->u.lval);