diff --git a/tinyexpr.c b/tinyexpr.c
index 176e8d0..ebf8dfe 100755
--- a/tinyexpr.c
+++ b/tinyexpr.c
@@ -87,7 +87,7 @@ typedef struct state {
 static te_expr *new_expr(const int type, const te_expr *parameters[]) {
     const int arity = ARITY(type);
     const int psize = sizeof(void*) * arity;
-    const int size = (sizeof(te_expr) - sizeof(void*)) + psize + (IS_CLOSURE(type) ? sizeof(void*) : 0);
+    const int size = sizeof(te_expr) + sizeof(void*) * (arity > 0 ? arity - 1 : 0) + (IS_CLOSURE(type) ? sizeof(void*) : 0);
     te_expr *ret = malloc(size);
     CHECK_NULL(ret);