diff --git a/.jenkins.d/README.md b/.jenkins.d/README.md
index 956ae18..3bacba8 100644
--- a/.jenkins.d/README.md
+++ b/.jenkins.d/README.md
@@ -28,3 +28,6 @@
 
   * empty: default build process
   * `code-coverage` (Linux OS is assumed): build process with code coverage analysis
+
+- `CACHE_DIR`: the variable defines a path to folder containing cached files from previous builds,
+  e.g., a compiled version of ndn-cxx library.  If not set, `/tmp` is used.