diff --git a/tests/daikon-tests/Makefile b/tests/daikon-tests/Makefile
index 3342685d6..b2c64fc0e 100644
--- a/tests/daikon-tests/Makefile
+++ b/tests/daikon-tests/Makefile
@@ -2,7 +2,10 @@
 # Read Makefile in parent directory to see what this all means
 
 # DAIKONDIR is the clone of the 'daikon' project.
-DAIKONDIR ?= $(realpath $(dir $(lastword ${MAKEFILE_LIST}))..)
+# See tests/Makefile.common for why this does not use '?='.
+ifeq ($(origin DAIKONDIR), undefined)
+  DAIKONDIR := $(realpath $(dir $(lastword ${MAKEFILE_LIST}))../..)
+endif
 SCRIPTS=${DAIKONDIR}/scripts
 
 # Help system