diff --git a/llvm/tools/CMakeLists.txt b/llvm/tools/CMakeLists.txt
index 203169350c53..aca4350fcb28 100644
--- a/llvm/tools/CMakeLists.txt
+++ b/llvm/tools/CMakeLists.txt
@@ -30,6 +30,10 @@ if(CYGWIN OR NOT LLVM_ENABLE_PIC)
   set(LLVM_TOOL_LLVM_LTO_BUILD Off)
 endif()
 
+# Add LTO before clang, ExternalProject requires targets specified in DEPENDS
+# to exist before the call to ExternalProject_Add
+add_llvm_tool_subdirectory(lto)
+
 # Projects supported via LLVM_EXTERNAL_*_SOURCE_DIR need to be explicitly
 # specified.
 add_llvm_external_project(clang)