diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index a078ec9..b78e7a7 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -33,6 +33,9 @@ endif(APPLE)
 
 ## Preferentially build the bundled code. Full vendoring is to follow in a later version.
 
+# Bundled code will occasionally use identical options - eg, BUILD_TESTING.
+set(BUILD_TESTING OFF)
+
 # Bundled liblzma
 set(XZ_MICROLZMA_DECODER OFF)
 set(XZ_MICROLZMA_ENCODER OFF)