diff --git a/library/x509_crt.c b/library/x509_crt.c
index 0330097..eabafe9 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1652,10 +1652,10 @@
     memset(&sb, 0, sizeof(sb));
 
     while ((entry = readdir(dir)) != NULL) {
-        snp_ret = mbedtls_snprintf(entry_name, sizeof entry_name,
+        snp_ret = mbedtls_snprintf(entry_name, sizeof(entry_name),
                                    "%s/%s", path, entry->d_name);
 
-        if (snp_ret < 0 || (size_t) snp_ret >= sizeof entry_name) {
+        if (snp_ret < 0 || (size_t) snp_ret >= sizeof(entry_name)) {
             ret = MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
             goto cleanup;
         } else if (stat(entry_name, &sb) == -1) {