diff --git a/.gitignore b/.gitignore
index fb607332..88555cd6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@ config-base-*
 macbook12-spi-driver-*.tar
 macbook12-spi-driver-*.tar.gz.UNTRUSTED
 pkgs
+spi.sha256
diff --git a/Makefile b/Makefile
index a497b7c0..b78f077c 100644
--- a/Makefile
+++ b/Makefile
@@ -97,8 +97,8 @@ $(SRC_TARFILE): $(SRC_FILE)$(UNTRUSTED_SUFF) $(HASH_FILE)
 endif
 
 $(SPI_SRC_TARFILE): $(SPI_SRC_TARFILE)$(UNTRUSTED_SUFF)
-	cat $< | sha256sum | head -c64 | grep -q "^$(SPI_HASH_SHA256)$$"
-	mv $< $@
+	$(file > spi.sha256,$(SPI_HASH_SHA256)  $(SPI_SRC_TARFILE)$(UNTRUSTED_SUFF))
+	sha256sum -c spi.sha256 && mv $< $@ && rm spi.sha256
 
 $(SRC_FILE)$(UNTRUSTED_SUFF):
 	@$(FETCH_CMD) $@ -- $(URL)