diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1501240..5235910 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -351,7 +351,7 @@
 endif()
 
 if (NOT EXISTS "${MBEDTLS_FRAMEWORK_DIR}/CMakeLists.txt")
-    if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.git/")
+    if (EXISTS "${MBEDTLS_DIR}/.git")
         message(FATAL_ERROR "${MBEDTLS_FRAMEWORK_DIR}/CMakeLists.txt not found (and does appear to be a git checkout). Run `git submodule update --init` from the source tree to fetch the submodule contents.")
     else ()
         message(FATAL_ERROR "${MBEDTLS_FRAMEWORK_DIR}/CMakeLists.txt not found (and does not appear to be a git checkout). Please ensure you have downloaded the right archive from the release page on GitHub.")