diff --git a/data/certs/master.ldap.test.crt b/data/certs/master.ldap.test.crt
index d81c083b..c63cc31f 100644
--- a/data/certs/master.ldap.test.crt
+++ b/data/certs/master.ldap.test.crt
@@ -1,31 +1,32 @@
 -----BEGIN CERTIFICATE-----
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-BQAwKzENMAsGA1UECgwEdGVzdDENMAsGA1UECwwEc3NzZDELMAkGA1UEAwwCY2Ew
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-asZaEzeO/9Yg3s/QK0E/ng==
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+4G73QYv83na29/6HjRoZhySCSUlrdGgiHWOQL1NxmKu/WD898kQx9w8sYYSxRyeO
+ZOGsukgRcTCqp9NGZCjH7LlP9ToU0BEpmVrgU0oN/ZQTBRnDl8Iaccz+dATz/93u
+G7ATKGNphIBEgXs8pMxlz3I=
 -----END CERTIFICATE-----
diff --git a/src/tools/gen-certs.sh b/src/tools/gen-certs.sh
index a70869d4..250371e2 100755
--- a/src/tools/gen-certs.sh
+++ b/src/tools/gen-certs.sh
@@ -22,11 +22,30 @@ mkdir -p $OUT
 # Create non-encrypted self-signed root certificate authority
 openssl req -new -x509 -days 7200 -config "$REQ_CONFIG" -subj "$SUBJECT/CN=ca" -keyout "$OUT/ca.key" -out "$OUT/ca.crt"
 
+# Extra names a service certificate must also be valid for, besides its own
+# hostname. master2.ldap.test is an alias of master.ldap.test, used by failover
+# topologies that need two distinct LDAP server names.
+declare -A ALIASES=(
+    [master.ldap.test]="master2.ldap.test"
+)
+
 # Create certificates
 for service in master.ldap.test dc.samba.test master.keycloak.test; do
+    # Modern TLS stacks match the hostname against subjectAltName and ignore
+    # CN, so each certificate lists its own name as a SAN as well.
+    san="DNS:$service"
+    for alias in ${ALIASES[$service]}; do
+        san="$san,DNS:$alias"
+    done
+
+    # The base extensions are shared, the SAN is per service.
+    ext="$OUT/$service.ext"
+    cp "$X509_CONFIG" "$ext"
+    echo "subjectAltName=$san" >> "$ext"
+
     openssl req -new -config "$REQ_CONFIG" -subj "$SUBJECT/CN=$service" -keyout "$OUT/$service.key" -out "$OUT/$service.csr"
-    openssl x509 -req -days 7200 -extfile "$X509_CONFIG" -CA "$OUT/ca.crt" -CAkey "$OUT/ca.key" -CAcreateserial -in "$OUT/$service.csr" -out "$OUT/$service.crt"
-    rm -f "$OUT/$service.csr"
+    openssl x509 -req -days 7200 -extfile "$ext" -CA "$OUT/ca.crt" -CAkey "$OUT/ca.key" -CAcreateserial -in "$OUT/$service.csr" -out "$OUT/$service.crt"
+    rm -f "$OUT/$service.csr" "$ext"
 done
 
 rm -f "$OUT/ca.srl"