diff --git a/include/nuttx/lib/math32.h b/include/nuttx/lib/math32.h
index 84289311d87..acfd09749f6 100644
--- a/include/nuttx/lib/math32.h
+++ b/include/nuttx/lib/math32.h
@@ -133,9 +133,9 @@ extern "C"
 #    define __umul64_const(res, m, n, bias) \
       do \
         { \
-          uint32_t __m_lo = (m); \
+          uint32_t __m_lo = (m) & 0xffffffff; \
           uint32_t __m_hi = (m) >> 32; \
-          uint32_t __n_lo = (n); \
+          uint32_t __n_lo = (n) & 0xffffffff; \
           uint32_t __n_hi = (n) >> 32; \
           uint32_t __res_lo; \
           uint32_t __res_hi; \