diff --git a/core/clang/config.mk b/core/clang/config.mk
index d44be526b..227169d4e 100644
--- a/core/clang/config.mk
+++ b/core/clang/config.mk
@@ -6,6 +6,11 @@ WITHOUT_TARGET_CLANG := true
 WITHOUT_HOST_CLANG := true
 endif
 
+# We don't have 64-bit host prebuilts yet.
+ifeq (true,$(HOST_IS_64_BIT))
+FORCE_BUILD_LLVM_COMPONENTS := true
+endif
+
 LLVM_PREBUILTS_PATH := prebuilts/clang/$(BUILD_OS)-x86/host/3.5/bin
 LLVM_PREBUILTS_HEADER_PATH := prebuilts/clang/$(BUILD_OS)-x86/host/3.5/lib/clang/3.5/include/
 
diff --git a/core/config.mk b/core/config.mk
index 84ff3fea4..287944e96 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -358,7 +358,7 @@ endif
 # ---------------------------------------------------------------
 # Generic tools.
 
-LEX := prebuilts/misc/$(BUILD_OS)-$(BUILD_ARCH)/flex/flex-2.5.39
+LEX := prebuilts/misc/$(BUILD_OS)-$(HOST_PREBUILT_ARCH)/flex/flex-2.5.39
 # The default PKGDATADIR built in the prebuilt bison is a relative path
 # external/bison/data.
 # To run bison from elsewhere you need to set up enviromental variable