diff --git a/README.md b/README.md
index b50e75cafc..df6365ca48 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,9 @@ By default `oqs-sys` attempts to find a system-provided version of `liboqs` and
 falling back to vendored from-source build otherwise.
 You can opt into forcing the vendored build by enabling the `vendored` feature.
 
+Otherwise, if you want to force using the system-provided `liboqs`,
+you can set the `LIBOQS_NO_VENDOR=1` environment variable and the build will fail if the library is not found.
+
 Serde support
 -------------