diff --git a/include/mbedtls/x509_internal.h b/include/mbedtls/x509_internal.h
index 7729108..6ca3db5 100644
--- a/include/mbedtls/x509_internal.h
+++ b/include/mbedtls/x509_internal.h
@@ -37,8 +37,11 @@
 #define MBEDTLS_X509_CACHE_FRAME_READERS_MAX ((uint32_t) -1)
 typedef struct mbedtls_x509_crt_cache
 {
+#if !defined(MBEDTLS_X509_ALWAYS_FLUSH) || \
+    defined(MBEDTLS_THREADING_C)
     uint32_t frame_readers;
     uint32_t pk_readers;
+#endif /* !MBEDTLS_X509_ALWAYS_FLUSH || MBEDTLS_THREADING_C */
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_threading_mutex_t frame_mutex;
     mbedtls_threading_mutex_t pk_mutex;