diff --git a/Makefile b/Makefile
index 10afe19ab03e6a1afbf1a4eccbc2681992ab6469..11427dbaff360687471b1eae915983cd51261c94 100644
--- a/Makefile
+++ b/Makefile
@@ -8,8 +8,8 @@ tmm:
 	make KERNEL_DIR=$(KERNEL_DIR) -C tmm_driver/src
 
 seal:
-	make -C sealing_key/src
+	make KERNEL_DIR=$(KERNEL_DIR) -C sealing_key/src
 
 clean:
-	make clean -C tmm_driver/src
-	make clean -C sealing_key/src
+	make clean KERNEL_DIR=$(KERNEL_DIR) -C tmm_driver/src
+	make clean KERNEL_DIR=$(KERNEL_DIR) -C sealing_key/src
diff --git a/sealing_key/src/Makefile b/sealing_key/src/Makefile
index 5df4ddc53bb75f8a62e64208f14945ef328568e8..5a1e5732a0910651be2a2fb23dbf8e18c33252c8 100644
--- a/sealing_key/src/Makefile
+++ b/sealing_key/src/Makefile
@@ -1,7 +1,7 @@
 obj-m += sealing_key.o
 # Otherwise we were called directly from the command
 # line; invoke the kernel build system.
-KERNEL_DIR=/usr/src/kernels/$(shell uname -r)
+KERNEL_DIR ?= /usr/src/kernels/$(shell uname -r)
 PWD:=$(shell pwd)
 
 modules: