diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 43dcdb53c4..6d5c8908a8 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1521,6 +1521,10 @@ system:gcc:ossl3:trixie:amd64:
       artifacts: true
 
 unit:gcc:ossl3:amd64:
+  # Set up environment variables to run unit tests with PKCS#11-aware OpenSSL
+  variables:
+    OPENSSL_CONF: "/var/tmp/etc/openssl-provider.cnf"
+    SOFTHSM2_CONF: "/var/tmp/softhsm2/softhsm2.conf"
   <<: *debian_trixie_amd64_image
   <<: *unit_test_job
   needs:
diff --git a/tests/dns/dnstap_test.c b/tests/dns/dnstap_test.c
index b2d1d01019..4c5133a855 100644
--- a/tests/dns/dnstap_test.c
+++ b/tests/dns/dnstap_test.c
@@ -18,6 +18,7 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <unistd.h>
 
 #define UNIT_TESTING
@@ -61,6 +62,7 @@ setup(void **state) {
 	 * the testdata was originally generated.
 	 */
 	setenv("TZ", "PDT8", 1);
+	tzset();
 
 	setup_loopmgr(state);
 
diff --git a/tests/dns/update_test.c b/tests/dns/update_test.c
index 496d5cdb45..eee86283d5 100644
--- a/tests/dns/update_test.c
+++ b/tests/dns/update_test.c
@@ -48,6 +48,7 @@ setup_test(void **state) {
 	UNUSED(state);
 
 	setenv("TZ", "", 1);
+	tzset();
 
 	return 0;
 }
diff --git a/tests/isc/time_test.c b/tests/isc/time_test.c
index 18b42e5098..de68b1fa47 100644
--- a/tests/isc/time_test.c
+++ b/tests/isc/time_test.c
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
@@ -144,6 +145,7 @@ ISC_RUN_TEST_IMPL(isc_time_parsehttptimestamp_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now();
 
 	isc_time_formathttptimestamp(&t, buf, sizeof(buf));
@@ -161,6 +163,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatISO8601_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now();
 
 	/* check formatting: yyyy-mm-ddThh:mm:ssZ */
@@ -195,6 +198,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatISO8601ms_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now();
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss.sssZ */
@@ -230,6 +234,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatISO8601us_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now_hires();
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss.ssssssZ */
@@ -265,6 +270,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatISO8601L_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now();
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss */
@@ -298,6 +304,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatISO8601Lms_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now();
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss.sss */
@@ -332,6 +339,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatISO8601Lus_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now_hires();
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss.ssssss */
@@ -366,6 +374,7 @@ ISC_RUN_TEST_IMPL(isc_time_formatshorttimestamp_test) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
+	tzset();
 	t = isc_time_now();
 
 	/* check formatting: yyyymmddhhmmsssss */