diff --git a/tracker-radar-tests/TR-domain-matching/domain_matching_tests.json b/tracker-radar-tests/TR-domain-matching/domain_matching_tests.json
index 6186e11..cfbf521 100644
--- a/tracker-radar-tests/TR-domain-matching/domain_matching_tests.json
+++ b/tracker-radar-tests/TR-domain-matching/domain_matching_tests.json
@@ -1077,6 +1077,62 @@
                 "expectAction": "redirect",
                 "expectRedirect": "data:application/javascript;base64,KGZ1bmN0aW9uKCkge3dpbmRvdy5zdXJyb2dhdGUxPXRydWV9KSgpOw==",
                 "expectExpression": "window.surrogate1 === true"
+            },
+            {
+                "name": "Encountering unknown surrogate with default:block should ignore",
+                "siteURL": "https://example.com",
+                "requestURL": "https://unknownsurrogates1.test/request1",
+                "requestType": "script",
+                "expectAction": "ignore"
+            },
+            {
+                "name": "Encountering unknown surrogate with default:ignore should ignore",
+                "siteURL": "https://example.com",
+                "requestURL": "https://unknownsurrogates2.test/request1",
+                "requestType": "script",
+                "expectAction": "ignore"
+            },
+            {
+                "name": "Encountering unknown surrogate with default:block and failing options check, should block",
+                "siteURL": "https://example.com",
+                "requestURL": "https://unknownsurrogates1.test/request2",
+                "requestType": "script",
+                "expectAction": "block"
+            },
+            {
+                "name": "Encountering unknown surrogate with default:block and successful options check, should ignore",
+                "siteURL": "https://selectedsite1.com",
+                "requestURL": "https://unknownsurrogates1.test/request2",
+                "requestType": "script",
+                "expectAction": "ignore"
+            },
+            {
+                "name": "Encountering unknown surrogate with default:ignore and failing options check, should ignore",
+                "siteURL": "https://example.com",
+                "requestURL": "https://unknownsurrogates2.test/request2",
+                "requestType": "script",
+                "expectAction": "ignore"
+            },
+            {
+                "name": "Encountering unknown surrogate with default:ignore and successful options check, should ignore",
+                "siteURL": "https://selectedsite1.com",
+                "requestURL": "https://unknownsurrogates2.test/request2",
+                "requestType": "script",
+                "expectAction": "ignore"
+            },
+            {
+                "name": "Encountering unknown surrogate with exemption (default:block) should ignore",
+                "siteURL": "https://exemptedsite1.com",
+                "requestURL": "https://unknownsurrogates1.test/request1",
+                "requestType": "script",
+                "expectAction": "ignore"
+            },
+            {
+                "name": "Encountering unknown surrogate with exemption (default:ignore) should ignore",
+                "siteURL": "https://exemptedsite1.com",
+                "requestURL": "https://unknownsurrogates2.test/request1",
+                "requestType": "script",
+                "expectAction": "ignore"
             }
         ]
     }
diff --git a/tracker-radar-tests/TR-domain-matching/tracker_radar_reference.json b/tracker-radar-tests/TR-domain-matching/tracker_radar_reference.json
index 9a831c9..1535d48 100644
--- a/tracker-radar-tests/TR-domain-matching/tracker_radar_reference.json
+++ b/tracker-radar-tests/TR-domain-matching/tracker_radar_reference.json
@@ -745,6 +745,74 @@
             ],
             "default": "block"
         },
+        "unknownsurrogates1.test": {
+            "domain": "unknownsurrogates1.test",
+            "owner": {
+                "name": "Test Site for Surrogates",
+                "displayName": "Surrogates Site",
+                "privacyPolicy": "",
+                "url": "http://blockedsurrogates.test"
+            },
+            "prevalence": 0.1,
+            "fingerprinting": 3,
+            "cookies": 0.1,
+            "categories": [],
+            "rules": [
+                {
+                    "rule": "unknownsurrogates1\\.test/request1",
+                    "surrogate": "unknownsurrogate1",
+                    "exceptions": {
+                        "domains": [
+                            "exemptedsite1.com"
+                        ]
+                    }
+                },
+                {
+                    "rule": "unknownsurrogates1\\.test/request2",
+                    "surrogate": "unknownsurrogate1",
+                    "options": {
+                        "domains": [
+                            "selectedsite1.com"
+                        ]
+                    }
+                }
+            ],
+            "default": "block"
+        },
+        "unknownsurrogates2.test": {
+            "domain": "unknownsurrogates2.test",
+            "owner": {
+                "name": "Test Site for Surrogates",
+                "displayName": "Surrogates Site",
+                "privacyPolicy": "",
+                "url": "http://blockedsurrogates.test"
+            },
+            "prevalence": 0.1,
+            "fingerprinting": 3,
+            "cookies": 0.1,
+            "categories": [],
+            "rules": [
+                {
+                    "rule": "unknownsurrogates2\\.test/request1",
+                    "surrogate": "unknownsurrogate2",
+                    "exceptions": {
+                        "domains": [
+                            "exemptedsite1.com"
+                        ]
+                    }
+                },
+                {
+                    "rule": "unknownsurrogates2\\.test/request2",
+                    "surrogate": "unknownsurrogate2",
+                    "options": {
+                        "domains": [
+                            "selectedsite1.com"
+                        ]
+                    }
+                }
+            ],
+            "default": "ignore"
+        },
         "format.test": {
             "domain": "format.test",
             "owner": {
@@ -861,7 +929,9 @@
             "domains": [
                 "other-surrogates.test",
                 "surrogates.test",
-                "blockedsurrogates.test"
+                "blockedsurrogates.test",
+                "unknownsurrogates1.test",
+                "unknownsurrogates2.test"
             ],
             "prevalence": 0.1,
             "displayName": "Test Site for Surrogates"
@@ -896,6 +966,8 @@
         "sub.ignore.test": "Ignore Site for Tracker Blocking",
         "surrogates.test": "Test Site for Surrogates",
         "other-surrogates.test": "Test Site for Surrogates",
-        "blockedsurrogates.test": "Test Site for Surrogates"
+        "blockedsurrogates.test": "Test Site for Surrogates",
+        "unknownsurrogates1.test": "Test Site for Surrogates",
+        "unknownsurrogates2.test": "Test Site for Surrogates"
     }
 }