diff --git a/Makefile b/Makefile
index 7978d04ee3e42ddc03eedabd64703326936d0d93..945064395f9c48d749ef0b4d179c9bf9b0e7b66e 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@
 # We have a problem here: this package may be a submodule of something
 # else (for example: fine-delay). If this is the case, fmc-bus is on ../
 # This external script returns the pathname of the "kernel" subdir of fmc-bus
-FMC_DRV = $(./check-fmc-bus)
+FMC_DRV ?= $(./check-fmc-bus)
 
 DIRS = $(FMC_DRV) kernel tools