diff --git a/library/x509_crt.c b/library/x509_crt.c
index b40bad2..2cbced2 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1599,7 +1599,7 @@
 cleanup:
     FindClose(hFind);
 #else /* !_WIN32_WINNT_XP */
-#error mbedtls_x509_crt_parse_path not available before Windows XP
+#error "mbedtls_x509_crt_parse_path not available before Windows XP"
 #endif /* !_WIN32_WINNT_XP */
 #else /* _WIN32 */
     int t_ret;