diff --git a/CHANGES.md b/CHANGES.md
index 18319f5..e75fd26 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -4,6 +4,9 @@
 - Minimal OCaml version is now 4.04.
 - Make colored output and JUnit features more prominent in the documentation.
   (Closes: #13, #12)
+- Increase default timeouts, so that they work as well for slow architecture
+  like s390x. The fastest timeout is now 20s (immediate test) and the longest
+  is 1h (huge test). (Closes: #18)
 
 ## v2.2.2 - 2020-01-24
 
diff --git a/src/lib/ounit2/advanced/oUnitTest.ml b/src/lib/ounit2/advanced/oUnitTest.ml
index 0baee14..4aa8885 100644
--- a/src/lib/ounit2/advanced/oUnitTest.ml
+++ b/src/lib/ounit2/advanced/oUnitTest.ml
@@ -98,10 +98,10 @@ type test =
 
 let delay_of_length =
   function
-    | Immediate -> 1.0
-    | Short -> 60.0
-    | Long -> 600.0
-    | Huge -> 1800.0
+    | Immediate -> 20.0 (* 20 seconds *)
+    | Short -> 600.0 (* 10 minutes *)
+    | Long -> 1800.0 (* 30 minutes *)
+    | Huge -> 3600.0 (* 1 hour *)
     | Custom_length f -> f
 
 let get_shard_id test_ctxt =