diff --git a/CMakeLists.txt b/CMakeLists.txt
index 64c0c9f..f577a30 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -161,4 +161,6 @@ add_custom_target(pd-clang-format
 )
 
 add_subdirectory(backends)
-add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/tests)
+if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+    add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/tests)
+endif()
diff --git a/source/drivers/os.cpp b/source/drivers/os.cpp
index b6971dd..5fc2d7f 100755
--- a/source/drivers/os.cpp
+++ b/source/drivers/os.cpp
@@ -10,7 +10,7 @@ PD_API u64 OsDriver::GetTime() const {
 }
 
 PD_API u64 OsDriver::GetTimeNano() const {
-  return std::chrono::duration_cast<std::chrono::milliseconds>(
+  return std::chrono::duration_cast<std::chrono::nanoseconds>(
              std::chrono::steady_clock::now().time_since_epoch())
       .count();
 }