diff --git a/tests-extra/tests/basic/nsec3/test.py b/tests-extra/tests/basic/nsec3/test.py
index 8a304a32b..0dd1be56b 100644
--- a/tests-extra/tests/basic/nsec3/test.py
+++ b/tests-extra/tests/basic/nsec3/test.py
@@ -16,6 +16,8 @@ t.link(zone, knot)
 t.link(zone, bind)
 
 t.start()
+knot.zone_wait(zone)
+bind.zone_wait(zone)
 
 # B1. Answer.
 resp = knot.dig("x.w.example", "MX", dnssec=True)
diff --git a/tests-extra/tests/catalog/rapid_updates/test.py b/tests-extra/tests/catalog/rapid_updates/test.py
index 35c6455be..ff44f9479 100644
--- a/tests-extra/tests/catalog/rapid_updates/test.py
+++ b/tests-extra/tests/catalog/rapid_updates/test.py
@@ -18,6 +18,9 @@ t = Test(stress=False)
 
 knot = t.server("knot")
 
+if knot.valgrind:
+    knot.semantic_check = False
+
 catz = t.zone("catalog1.", storage=".")
 
 t.link(catz, knot)
diff --git a/tests-extra/tests/ixfr/knot_knot/test.py b/tests-extra/tests/ixfr/knot_knot/test.py
index ee9ec0e92..22086e4e9 100644
--- a/tests-extra/tests/ixfr/knot_knot/test.py
+++ b/tests-extra/tests/ixfr/knot_knot/test.py
@@ -12,6 +12,10 @@ zones = t.zone_rnd(5, records=50) + t.zone("records.")
 
 t.link(zones, master, slave, ixfr=True)
 
+if master.valgrind:
+    master.semantic_check = False
+    slave.semantic_check = False
+
 master.tcp_io_timeout = 3000
 slave.tcp_io_timeout = 3000
 slave.tcp_remote_io_timeout = 8000
diff --git a/tests-extra/tests/modules/dnsproxy/test.py b/tests-extra/tests/modules/dnsproxy/test.py
index 3d6f4287e..fa506c133 100644
--- a/tests-extra/tests/modules/dnsproxy/test.py
+++ b/tests-extra/tests/modules/dnsproxy/test.py
@@ -24,6 +24,10 @@ remote = t.server("knot")
 t.link(zone_common2, remote)
 t.link(zone_remote, remote)
 
+if local.valgrind:
+    local.semantic_check = False
+    remote.semantic_check = False
+
 def is_subzone(subzone, zone):
     """Tests if the first zone is a subzone of the second one or equal, case insensitive."""
     return subzone.name.lower().endswith(zone.name.lower())
diff --git a/tests-extra/tests/modules/stats/test.py b/tests-extra/tests/modules/stats/test.py
index 9b9986366..c800f69a5 100644
--- a/tests-extra/tests/modules/stats/test.py
+++ b/tests-extra/tests/modules/stats/test.py
@@ -58,7 +58,7 @@ knot.add_module(zones[0], ModStats())
 knot.add_module(zones[1], ModStats())
 
 t.start()
-t.sleep(4)
+t.zones_wait(zones)
 
 check_item(knot, "server", "zone-count", 2)
 
diff --git a/tests-extra/tests/zone/backup/test.py b/tests-extra/tests/zone/backup/test.py
index a8acf1e24..b96383bca 100644
--- a/tests-extra/tests/zone/backup/test.py
+++ b/tests-extra/tests/zone/backup/test.py
@@ -43,6 +43,10 @@ zone0_expire = 45   # zone zones[0] expiration time in its SOA
 valgrind_delay = 2 if slave.valgrind else 0  # allow a little time margin under Valgrind
 valgrind_delay += 2 # even without valgrind, add some tolerance because rounding timestamps to whole seconds multiple times
 
+if master.valgrind:
+    master.semantic_check = False
+    slave.semantic_check = False
+
 t.start()
 serials_init = slave.zones_wait(zones)
 start_time = int(t.uptime())
diff --git a/tests-extra/tests/zone/backup_lock/test.py b/tests-extra/tests/zone/backup_lock/test.py
index 15c4e8c9f..1aab2b550 100644
--- a/tests-extra/tests/zone/backup_lock/test.py
+++ b/tests-extra/tests/zone/backup_lock/test.py
@@ -59,6 +59,10 @@ if master.valgrind:
 lockfile = os.path.join(backup_dir, "lock.knot_backup")
 labelfile = os.path.join(backup_dir, "knot_backup.label")
 
+if master.valgrind:
+    master.semantic_check = False
+    master2.semantic_check = False
+
 t.start()
 serials_init = master.zones_wait(zones)
 
diff --git a/tests-extra/tests/zone/flush_immediate/test.py b/tests-extra/tests/zone/flush_immediate/test.py
index d2ab1828e..9e2f18708 100644
--- a/tests-extra/tests/zone/flush_immediate/test.py
+++ b/tests-extra/tests/zone/flush_immediate/test.py
@@ -17,6 +17,10 @@ master.dnssec(zone).enable = True
 master.zonefile_sync = 0
 slave.zonefile_sync = 0
 
+if master.valgrind:
+    master.semantic_check = False
+    slave.semantic_check = False
+
 t.start()
 
 m_zfpath = master.zones[zone[0].name].zfile.path