diff --git a/db/src/models/availability_changeset.rs b/db/src/models/availability_changeset.rs
index ab5d4f15..281bd30a 100644
--- a/db/src/models/availability_changeset.rs
+++ b/db/src/models/availability_changeset.rs
@@ -61,13 +61,14 @@ fn time_is_not_already_made_available(
         ));
     }
 
-    let free_block_found_for_start = free_slots.iter().any(|s| s.0 <= *start && s.1 >= *start);
-    let free_block_found_for_end = free_slots.iter().any(|s| s.0 <= *end && s.1 >= *end);
+    let free_block_found = free_slots
+        .iter()
+        .any(|s| s.0 <= *start && *start <= s.1 && s.0 <= *end && *end <= s.1);
     let is_already_present_as_is = existing_availabilities
         .iter()
         .any(|a| a.start == *start && a.end == *end);
 
-    if !free_block_found_for_start || !free_block_found_for_end || is_already_present_as_is {
+    if !free_block_found || is_already_present_as_is {
         return Err(AsyncValidateError::new(
             "Verfügbarkeit kann nicht erstellt werden, da eine vorhandene Verfügbarkeit überschnitten würde.",
         ));
diff --git a/web/src/endpoints/availability/post_new.rs b/web/src/endpoints/availability/post_new.rs
index 86577460..cfceabc5 100644
--- a/web/src/endpoints/availability/post_new.rs
+++ b/web/src/endpoints/availability/post_new.rs
@@ -131,7 +131,7 @@ mod tests {
     }
 
     #[db_test]
-    async fn cant_create_availability_for_myself_when_time_slot_already_present(
+    async fn cant_create_availability_for_myself_when_time_slot_already_present_exactly(
         context: &DbTestContext,
     ) {
         let app = context.app().await;
@@ -151,6 +151,28 @@ mod tests {
         assert_eq!(StatusCode::UNPROCESSABLE_ENTITY, response.status());
     }
 
+    #[db_test]
+    async fn cant_create_availability_for_myself_when_time_slot_already_present_partly(
+        context: &DbTestContext,
+    ) {
+        let app = context.app().await;
+
+        let config = RequestConfig::new("/availability/new");
+        create_test_login_user(&context.db_pool, &config).await;
+
+        let date = Faker.fake();
+        let changeset = AvailabilityChangeset::create_for_test(&date, 10, 20);
+        Availability::create(&context.db_pool, 1, &changeset)
+            .await
+            .unwrap();
+
+        let mut form = create_form(&date, 10, 20, None);
+        form.enddate = form.startdate.succ_opt().unwrap();
+        let response = test_post(app, &config, Some(form)).await;
+
+        assert_eq!(StatusCode::UNPROCESSABLE_ENTITY, response.status());
+    }
+
     #[db_test]
     async fn create_new_updates_existing_when_time_slots_connect(context: &DbTestContext) {
         let app = context.app().await;