diff --git a/src/hb.hh b/src/hb.hh
index 82e19422c..f567f26a1 100644
--- a/src/hb.hh
+++ b/src/hb.hh
@@ -442,9 +442,9 @@ static int HB_UNUSED _hb_errno = 0;
 #define HB_STMT_END   while (0)
 
 /* Static-assert as expression. */
-template <unsigned int cond> class hb_assert_constant_t;
-template <> class hb_assert_constant_t<1> {};
-#define ASSERT_STATIC_EXPR_ZERO(_cond) (0 * (unsigned int) sizeof (hb_assert_constant_t<_cond>))
+template <bool cond> class hb_assert_constant_t;
+template <> class hb_assert_constant_t<true> {};
+#define ASSERT_STATIC_EXPR_ZERO(_cond) (0u * (unsigned int) sizeof (hb_assert_constant_t<_cond>))
 
 /* Lets assert int types.  Saves trouble down the road. */
 static_assert ((sizeof (int8_t) == 1), "");