diff --git a/tools/concrete-protocol/CMakeLists.txt b/tools/concrete-protocol/CMakeLists.txt
index db358904c..ccf084a4b 100644
--- a/tools/concrete-protocol/CMakeLists.txt
+++ b/tools/concrete-protocol/CMakeLists.txt
@@ -20,6 +20,7 @@ ExternalProject_Add(
   GIT_TAG release-${CAPNP_VERSION}
   GIT_SUBMODULES_RECURSE ON
   GIT_PROGRESS   TRUE
+  UPDATE_DISCONNECTED TRUE
   BUILD_ALWAYS 1
   INSTALL_COMMAND cp ${CAPNP_LIB_DIR}/capnp/${CAPNP_LIBRARY} ${CAPNP_LIB_DIR}/capnp/${CAPNP_JSON_LIBRARY} ${CAPNP_LIB_DIR}/kj/${KJ_LIBRARY} ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
   BINARY_DIR ${CAPNP_BIN_DIR}