diff --git a/src/main/cljc/org/domaindrivenarchitecture/activity_pub_poc/core.cljc b/src/main/cljc/org/domaindrivenarchitecture/activity_pub_poc/core.cljc
index d725f0c..1119898 100644
--- a/src/main/cljc/org/domaindrivenarchitecture/activity_pub_poc/core.cljc
+++ b/src/main/cljc/org/domaindrivenarchitecture/activity_pub_poc/core.cljc
@@ -24,10 +24,12 @@
          {k (first (normalize-value v))}
          :else {k (normalize-value v)})))
 
-(defn serialize
-  [as-map]
-  (json/write-str
-   (merge
-    {(keyword "@context") "https://www.w3.org/ns/activitystreams"}
-    (walk/walk normalize-functional-property identity as-map))
-   :escape-slash false))
\ No newline at end of file
+(defn-spec serialize string?
+  [spec s/spec?
+   as-map map?]
+  (let [speced-map (assert (s/valid? spec as-map))]
+    (json/write-str
+     (merge
+      {(keyword "@context") "https://www.w3.org/ns/activitystreams"}
+      (walk/walk normalize-functional-property identity speced-map))
+     :escape-slash false)))
\ No newline at end of file
diff --git a/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2_test.cljc b/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2_test.cljc
index aca1290..bd1096d 100644
--- a/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2_test.cljc
+++ b/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2_test.cljc
@@ -6,6 +6,7 @@
 
 (deftest id-test
   (is (s/valid? ::sut/id "https://social.bla/alyssa/status/RANDOMHASH"))
+  (is (s/valid? ::sut/id ["https://social.bla/alyssa/status/RANDOMHASH"]))
   (is (not (s/valid? ::sut/id nil)))
   (is (not (s/valid? ::sut/id 2)))
   (is (not (s/valid? ::sut/id "https://no-uri:abc")))
diff --git a/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/core_test.cljc b/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/core_test.cljc
index 78498a9..eb06645 100644
--- a/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/core_test.cljc
+++ b/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/core_test.cljc
@@ -17,6 +17,7 @@
                "\"name\":\"Sally\"},"
                "\"object\":\"http://example.org/notes/1\"}")
           (sut/serialize
+           ::as/Like
            {::as/id ["http://example.org/likes/1"]
             ::as/summary "Sally liked a note",
             ::as/type "Like",
diff --git a/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/xsd_test.cljc b/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/xsd_test.cljc
new file mode 100644
index 0000000..56bfcca
--- /dev/null
+++ b/src/test/cljc/org/domaindrivenarchitecture/activity_pub_poc/xsd_test.cljc
@@ -0,0 +1,6 @@
+(ns org.domaindrivenarchitecture.activity-pub-poc.xsd-test
+  (:require
+   [clojure.test :refer [deftest is are testing run-tests]]
+   [clojure.spec.test.alpha :as st]
+   [clojure.spec.alpha :as s]
+   [org.domaindrivenarchitecture.activity-pub-poc.xsd :as sut]))
\ No newline at end of file