diff --git a/test/unit/lib/blob/Makefile b/test/unit/lib/blob/Makefile
index 516a8f758..6a47d4372 100644
--- a/test/unit/lib/blob/Makefile
+++ b/test/unit/lib/blob/Makefile
@@ -34,17 +34,24 @@
 SPDK_ROOT_DIR := $(abspath $(CURDIR)/../../../..)
 include $(SPDK_ROOT_DIR)/mk/spdk.common.mk
 
-HASH = \#
-CUNIT_VERSION = $(shell echo "$(HASH)include <CUnit/CUnit.h>" | $(CC) -E -dM - | sed -n -e 's/\#define CU_VERSION "\([0-9\.\-]*\).*/\1/p')
-ifeq ($(CUNIT_VERSION),2.1-3)
+#  Make targets are based on the current value of $(CUNIT_VERSION),
+#  rather than on configuration values. All sub-directories are
+#  added to $(DIRS-y) so that they are included in 'make clean'.
+#  $(ALL_DIRS) contains the list of sub-directories to compile.
 DIRS-y = blob.c
+ALL_DIRS =
+
+HASH = \#
+CUNIT_VERSION = $(shell echo "$(HASH)include <CUnit/CUnit.h>" | $(CC) $(CFLAGS) -E -dM - | sed -n -e 's/\#define CU_VERSION "\([0-9\.\-]*\).*/\1/p')
+ifeq ($(CUNIT_VERSION),2.1-3)
+ALL_DIRS = blob.c
 else
 $(warning "blob_ut.c compilation skipped, only CUnit version 2.1-3 is supported")
 endif
 
 .PHONY: all clean $(DIRS-y)
 
-all: $(DIRS-y)
+all: $(ALL_DIRS)
 clean: $(DIRS-y)
 
 include $(SPDK_ROOT_DIR)/mk/spdk.subdirs.mk