diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1c136c9..6371e46 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,7 +1,11 @@
 # cotire example project
 
+add_library(foo STATIC foo.cpp)
+target_include_directories(foo PUBLIC foo)
+
 add_library(acme STATIC acme.cpp)
 target_include_directories(acme PUBLIC acme)
+target_link_libraries(acme foo)
 
 add_executable(example main.cpp example.cpp log.cpp log.h example.h)
 
diff --git a/src/foo.cpp b/src/foo.cpp
new file mode 100644
index 0000000..2789e61
--- /dev/null
+++ b/src/foo.cpp
@@ -0,0 +1,3 @@
+#include "foo.h"
+
+int foo() { return 42; }
diff --git a/src/foo/foo.h b/src/foo/foo.h
new file mode 100644
index 0000000..5d5f8f0
--- /dev/null
+++ b/src/foo/foo.h
@@ -0,0 +1 @@
+int foo();
diff --git a/src/precompiled.h b/src/precompiled.h
index eb92a2b..5284f51 100644
--- a/src/precompiled.h
+++ b/src/precompiled.h
@@ -1,3 +1,5 @@
 #pragma once
 
 #include "acme.h"
+#include "foo.h"
+