diff --git a/depends/tthread/CMakeLists.txt b/depends/tthread/CMakeLists.txt
index 9e0e85dc5..dfb1d9901 100644
--- a/depends/tthread/CMakeLists.txt
+++ b/depends/tthread/CMakeLists.txt
@@ -1,5 +1,5 @@
 project(dfhack-tinythread)
-add_library(dfhack-tinythread STATIC EXCLUDE_FROM_ALL tinythread.cpp tinythread.h fast_mutex.h)
+add_library(dfhack-tinythread STATIC EXCLUDE_FROM_ALL tinythread.cpp tinythread.h)
 if(UNIX)
     target_link_libraries(dfhack-tinythread pthread)
 endif()