diff --git a/libc/test/UnitTest/CMakeLists.txt b/libc/test/UnitTest/CMakeLists.txt
--- a/libc/test/UnitTest/CMakeLists.txt
+++ b/libc/test/UnitTest/CMakeLists.txt
@@ -24,8 +24,12 @@
   HermeticTestUtils.cpp
 )
 
-foreach(lib LibcUnitTest LibcHermeticTest)
+foreach(lib LibcUnitTest LibcHermeticTest LibcTestMain)
   target_include_directories(${lib} PUBLIC ${LIBC_SOURCE_DIR})
+  if(LLVM_LIBC_FULL_BUILD)
+    # If we are in full build mode, then we should use our own public headers.
+    target_include_directories(${lib} PRIVATE ${LIBC_BUILD_DIR}/include)
+  endif()
   target_compile_options(${lib} PRIVATE ${LIBC_HERMETIC_TEST_COMPILE_OPTIONS}
                          -fno-exceptions -fno-rtti)
   add_dependencies(${lib}