diff --git a/p256-m.c b/p256-m.c
index 28b85cb..8653ae6 100644
--- a/p256-m.c
+++ b/p256-m.c
@@ -307,8 +307,8 @@ static uint64_t u32_muladd64(uint32_t x, uint32_t y, uint32_t z, uint32_t t)
     /* x = xl + 2**16 xh, y = yl + 2**16 yh */
     const uint16_t xl = (uint16_t) x;
     const uint16_t yl = (uint16_t) y;
-    const uint16_t xh = x >> 16;
-    const uint16_t yh = y >> 16;
+    const uint16_t xh = (uint16_t)(x >> 16);
+    const uint16_t yh = (uint16_t)(y >> 16);
 
     /* x*y = xl*yl + 2**16 (xh*yl + yl*yh) + 2**32 xh*yh
      *     = lo    + 2**16 (m1    + m2   ) + 2**32 hi    */