diff --git a/timezone/Makefile b/timezone/Makefile
index 998cd14..2f6e80e 100644
--- a/timezone/Makefile
+++ b/timezone/Makefile
@@ -85,6 +85,9 @@ GCONV_PATH=${common-objpfx}iconvdata LANGUAGE=C LC_ALL=C \
 $(evaluate-test)
 endef
 
+
+.NOTPARALLEL:
+
 $(objpfx)test-tz.out: $(addprefix $(testdata)/, America/New_York Etc/UTC UTC)
 $(objpfx)tst-timezone.out: $(addprefix $(testdata)/, \
 				       Europe/Berlin Universal \
@@ -102,7 +105,6 @@ $(testdata)/America/New_York: northamerica $(zic-deps)
 	$(build-testdata)
 $(testdata)/Etc/UTC: etcetera $(zic-deps)
 	$(build-testdata)
-# Use a pattern rule to indicate the command produces both targets at once.
 # Two separate targets built separately can collide if in parallel.
 %/UTC %/Universal: simplebackw $(zic-deps) %/Etc/UTC
 	$(build-testdata)