twiddle test for portability
diff --git a/regress/Makefile b/regress/Makefile
index 13e3fc8..860c53f 100644
--- a/regress/Makefile
+++ b/regress/Makefile
@@ -207,7 +207,7 @@
 unit:
 	set -e ; if test -z "${SKIP_UNIT}" ; then \
 		V="" ; \
-		test "x${USE_VALGRIND}" != "x" && \
+		test "x${USE_VALGRIND}" = "x" || \
 		    V=${.CURDIR}/valgrind-unit.sh ; \
 		$$V ${.OBJDIR}/unittests/sshbuf/test_sshbuf ; \
 		$$V ${.OBJDIR}/unittests/sshkey/test_sshkey \