diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 3b957733a4e0..b2035ac8920c 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for net selftests
 
-CFLAGS =  -Wall -Wl,--no-as-needed -O2 -g
+CFLAGS += -Wall -Wl,--no-as-needed -O2 -g
 CFLAGS += -I../../../../usr/include/ $(KHDR_INCLUDES)
 # Additional include paths needed by kselftest.h
 CFLAGS += -I../
diff --git a/tools/testing/selftests/net/openvswitch/Makefile b/tools/testing/selftests/net/openvswitch/Makefile
index 2f1508abc826..3fd1da2ec07d 100644
--- a/tools/testing/selftests/net/openvswitch/Makefile
+++ b/tools/testing/selftests/net/openvswitch/Makefile
@@ -2,7 +2,7 @@
 
 top_srcdir = ../../../../..
 
-CFLAGS =  -Wall -Wl,--no-as-needed -O2 -g -I$(top_srcdir)/usr/include $(KHDR_INCLUDES)
+CFLAGS += -Wall -Wl,--no-as-needed -O2 -g -I$(top_srcdir)/usr/include $(KHDR_INCLUDES)
 
 TEST_PROGS := openvswitch.sh