diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 1474f65f..c7f80afc 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -10,17 +10,11 @@ set(DMDFE_MINOR_VERSION   0)
 set(DMDFE_PATCH_VERSION   60)
 set(DMDFE_VERSION         ${D_VERSION}.${DMDFE_MINOR_VERSION}.${DMDFE_PATCH_VERSION})
 
-if(INCLUDE_INSTALL_DIR)
-    set(INCLUDE_INSTALL_DIR_DEFAULT ${INCLUDE_INSTALL_DIR})
-else()
-    set(INCLUDE_INSTALL_DIR_DEFAULT ${CMAKE_INSTALL_PREFIX}/include/d)
-endif()
-
 set(MULTILIB              OFF                                       CACHE BOOL    "Build both 32/64 bit runtime libraries")
 set(BUILD_BC_LIBS         OFF                                       CACHE BOOL    "Build the runtime as LLVM bitcode libraries")
 set(BUILD_SINGLE_LIB      ON                                        CACHE BOOL    "Build single runtime library (no core/rt/gc split)")
 set(LIB_SUFFIX            ""                                        CACHE STRING  "'64' to install libraries into ${PREFIX}/lib64")
-set(INCLUDE_INSTALL_DIR   ${INCLUDE_INSTALL_DIR_DEFAULT}            CACHE PATH    "Path to install D modules to")
+set(INCLUDE_INSTALL_DIR   ${CMAKE_INSTALL_PREFIX}/include/d         CACHE PATH    "Path to install D modules to")
 set(BUILD_SHARED_LIBS     OFF                                       CACHE BOOL    "Whether to build the runtime as a shared library (*UNSUPPORTED*)")
 set(D_FLAGS               -w;-d                                     CACHE STRING  "Runtime build flags, separated by ;")
 set(D_FLAGS_DEBUG         -g                                        CACHE STRING  "Runtime build flags (debug libraries), separated by ;")