diff --git a/deps/outliner/src/logseq/outliner/property.cljs b/deps/outliner/src/logseq/outliner/property.cljs
index 5a561ed96d..0358e7dbab 100644
--- a/deps/outliner/src/logseq/outliner/property.cljs
+++ b/deps/outliner/src/logseq/outliner/property.cljs
@@ -221,6 +221,12 @@
                       {:type :notification
                        :payload {:message "This property can't change from multiple values to one value because it has existing data."
                                  :type :warning}})))
+    (when (and (contains? changed-property-attrs :logseq.property/type)
+               (seq (d/datoms @conn :avet db-ident)))
+      (throw (ex-info "Disallowed type change with existing data"
+                      {:type :notification
+                       :payload {:message "This property's type can't be changed because it has existing data."
+                                 :type :error}})))
     (when (seq tx-data)
       (ldb/transact! conn tx-data {:outliner-op :update-property
                                    :property-id (:db/id property)}))
diff --git a/deps/outliner/test/logseq/outliner/property_test.cljs b/deps/outliner/test/logseq/outliner/property_test.cljs
index 057750d90c..1dcfa6910e 100644
--- a/deps/outliner/test/logseq/outliner/property_test.cljs
+++ b/deps/outliner/test/logseq/outliner/property_test.cljs
@@ -45,6 +45,20 @@
              (:block/title (d/entity @conn :user.property/p1-2)))
           "3rd property gets unique ident"))))
 
+(deftest upsert-property-rejects-type-change-with-existing-data
+  (testing "Changing type is rejected when property has values"
+    (let [conn (db-test/create-conn-with-blocks
+                [{:page {:block/title "page1"}
+                  :blocks [{:block/title "b1" :build/properties {:status "active"}}]}])]
+      (is (thrown-with-msg?
+           js/Error #"Disallowed type change with existing data"
+           (outliner-property/upsert-property! conn :user.property/status {:logseq.property/type :number} {})))))
+
+  (testing "Changing type is allowed when property has no values"
+    (let [conn (db-test/create-conn-with-blocks {:properties {:empty-prop {:logseq.property/type :default}}})]
+      (outliner-property/upsert-property! conn :user.property/empty-prop {:logseq.property/type :number} {})
+      (is (= :number (:logseq.property/type (d/entity @conn :user.property/empty-prop)))))))
+
 (deftest convert-property-input-string
   (testing "Convert property input string according to its schema type"
     (let [test-uuid (random-uuid)]