diff --git a/e_os.h b/e_os.h
index 49a0c3ed181c22e426f3399c1e9efd747a5f73d7..d331044eadaf01dae18821bd95c8f4edc6d8a71e 100644
--- a/e_os.h
+++ b/e_os.h
@@ -539,7 +539,7 @@ struct servent *getservbyname(const char *name, const char *proto);
 # endif
 /* end vxworks */
 
-#define OSSL_NELEM(x)    (sizeof(x)/sizeof(x[0]))
+#define OSSL_NELEM(x)    (sizeof(x)/sizeof((x)[0]))
 
 #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
 # define CRYPTO_memcmp memcmp