diff --git a/gtest.mk b/gtest.mk
index 39200b76..1d3f4c32 100644
--- a/gtest.mk
+++ b/gtest.mk
@@ -1,4 +1,4 @@
-## Copyright (C) 2010 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+## Copyright (C) 2011 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
 ##
 ## This program is free software; you can redistribute it and/or modify it
 ## under the terms of the GNU General Public License as published by the
@@ -16,7 +16,15 @@
 
 TEST_PROGS=
 
+#
+# NOTE: we set the locale/tz to some well-know values, so the tests
+# (at least when running under 'make check') run in a predictable
+# environment. There are specific tests different timezone, though.
+#
+
 test: all $(TEST_PROGS)
+	 @export LC_ALL="en_US.utf8"
+	 @export TZ="Europe/Helsinki"
 	 @test -z "$(TEST_PROGS)" || gtester --verbose $(TEST_PROGS) || exit $$?; \
 	 test -z "$(SUBDIRS)" || \
 		for subdir in $(SUBDIRS); do \