diff --git a/cpu/x86/uefi/build_uefi.sh b/cpu/x86/uefi/build_uefi.sh
index 5b7cba644..c49718f93 100755
--- a/cpu/x86/uefi/build_uefi.sh
+++ b/cpu/x86/uefi/build_uefi.sh
@@ -5,10 +5,17 @@ SCRIPT_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 # This script will always run on its own basepath, no matter where you call it from.
 pushd ${SCRIPT_DIR}
 
+if [ "$(uname -m)" = "x86_64" ]; then
+    export ARCH=X64
+fi
+
 # Download the UEFI tool and library sources:
-git clone --depth=1 https://github.com/tianocore/edk2 || exit
-# This script only supports building the tools on 64-bit hosts:
-export ARCH=X64
+if [ -e edk2 ]; then
+    make -C edk2/BaseTools/Source/C/Common clean
+    make -C edk2/BaseTools/Source/C/GenFw clean
+else
+    git clone --depth=1 https://github.com/tianocore/edk2 || exit
+fi
 # Build common sources required by the GenFw tool:
 make -C edk2/BaseTools/Source/C/Common || exit
 # Build the GenFw tool that is used to generate UEFI binaries: