diff --git a/arch/arm/src/samv7/sam_us.c b/arch/arm/src/samv7/sam_us.c
index aca0376617..a04c42cade 100644
--- a/arch/arm/src/samv7/sam_us.c
+++ b/arch/arm/src/samv7/sam_us.c
@@ -177,7 +177,7 @@ int sam_read_user_signature(void *buffer, size_t buflen)
 
   /* sam_eefc_readsequence requires read length in bit words. */
 
-  nwords = (buflen + sizeof(uint32_t) / sizeof(uint32_t));
+  nwords = (buflen + sizeof(uint32_t)) / sizeof(uint32_t);
   sam_eefc_readsequence(FCMD_STUS, FCMD_SPUS, g_page_buffer, nwords);
 
   /* Copy local buffer to void *buffer provided by the user. */