diff --git a/flang/runtime/CMakeLists.txt b/flang/runtime/CMakeLists.txt
--- a/flang/runtime/CMakeLists.txt
+++ b/flang/runtime/CMakeLists.txt
@@ -57,3 +57,5 @@
   LINK_LIBS
   FortranDecimal
 )
+
+target_include_directories(FortranRuntime PRIVATE ${CMAKE_CURRENT_BINARY_DIR})