diff --git a/CMakeLists.txt b/CMakeLists.txt
index d96afc4651775..8bd4c62231527 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -69,6 +69,9 @@ if(LLVM_PARALLEL_COMPILE_JOBS)
 endif()
 
 set(LLVM_BUILD_GLOBAL_ISEL OFF CACHE BOOL "Experimental: Build GlobalISel")
+if(LLVM_BUILD_GLOBAL_ISEL)
+  add_definitions(-DLLVM_BUILD_GLOBAL_ISEL)
+endif()
 
 set(LLVM_PARALLEL_LINK_JOBS "" CACHE STRING
   "Define the maximum number of concurrent link jobs.")