diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -348,7 +348,7 @@
 
 option(LLVM_ENABLE_THREADS "Use threads if available." ON)
 
-option(LLVM_ENABLE_ZLIB "Use zlib for compression/decompression if available." ON)
+set(LLVM_ENABLE_ZLIB "ON" CACHE STRING "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")
 
diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -175,6 +175,10 @@
   message(FATAL_ERROR "Failed to congifure libxml2")
 endif()
 
+if (LLVM_ENABLE_ZLIB STREQUAL "FORCE_ON" AND NOT HAVE_LIBZ)
+  message(FATAL_ERROR "Failed to configure zlib")
+endif()
+
 check_library_exists(xar xar_open "" HAVE_LIBXAR)
 if(HAVE_LIBXAR)
   set(XAR_LIB xar)