diff --git a/src/lib_shell/bootstrap_pipeline.ml b/src/lib_shell/bootstrap_pipeline.ml
index eb9c8ff4f82cfa5da5b52b26fc5be25d577f3fbb..3694c3bd0d84663d370850b5cfde06f3ce062bb6 100644
--- a/src/lib_shell/bootstrap_pipeline.ml
+++ b/src/lib_shell/bootstrap_pipeline.ml
@@ -143,8 +143,8 @@ type t = {
 
 (** A block is NOT acceptable if one of the following holds:
 
-    - The timestamp of the block is more than 15 seconds ahead in the
-   future.
+    - The timestamp of the block is more than s seconds in the
+   future, where s is specified by the module Clock_drift.
 
     - The block is at the same level as the checkpoint, but they are
    different.
diff --git a/src/lib_shell/clock_drift.ml b/src/lib_shell/clock_drift.ml
index 744953f0d0c5d724f49e365c668bbfde04edbeb5..ba40f08ea8a0c2e1f7b109e6364284fc61fd1fdf 100644
--- a/src/lib_shell/clock_drift.ml
+++ b/src/lib_shell/clock_drift.ml
@@ -22,7 +22,7 @@
 (*                                                                           *)
 (*****************************************************************************)
 
-let max_timestamp_drift : Ptime.span = Ptime.Span.of_int_s 15
+let max_timestamp_drift : Ptime.span = Ptime.Span.of_int_s 5
 
 let soon : unit -> Time.Protocol.t =
  fun () ->
diff --git a/tests_python/tests_008/test_forge_block.py b/tests_python/tests_008/test_forge_block.py
index 1aa64a36b47795418ce77dc446283378ebad2018..babcdeb1d04c0946c00954d4d27a58e11965e649 100755
--- a/tests_python/tests_008/test_forge_block.py
+++ b/tests_python/tests_008/test_forge_block.py
@@ -9,7 +9,7 @@ PROTO_DEMO = 'ProtoDemoNoopsDemoNoopsDemoNoopsDemoNoopsDemo6XBoYp'
 @pytest.mark.slow
 @pytest.mark.incremental
 class TestForgeBlock:
-    """ Check that a block more than 15 seconds in the future is rejected """
+    """ Check that a block more than 5 seconds in the future is rejected """
 
     def test_setup_network(self, sandbox: Sandbox):
         sandbox.add_node(1, params=constants.NODE_PARAMS)
@@ -21,7 +21,7 @@ class TestForgeBlock:
 
     def test_activate_proto_demo_time_shifted_ok(self, sandbox: Sandbox):
         parameters = {}  # type: dict
-        delta = datetime.timedelta(seconds=10)
+        delta = datetime.timedelta(seconds=5)
         sandbox.client(1).activate_protocol_json(
             PROTO_DEMO,
             parameters,
diff --git a/tests_python/tests_009/test_forge_block.py b/tests_python/tests_009/test_forge_block.py
index 1aa64a36b47795418ce77dc446283378ebad2018..babcdeb1d04c0946c00954d4d27a58e11965e649 100755
--- a/tests_python/tests_009/test_forge_block.py
+++ b/tests_python/tests_009/test_forge_block.py
@@ -9,7 +9,7 @@ PROTO_DEMO = 'ProtoDemoNoopsDemoNoopsDemoNoopsDemoNoopsDemo6XBoYp'
 @pytest.mark.slow
 @pytest.mark.incremental
 class TestForgeBlock:
-    """ Check that a block more than 15 seconds in the future is rejected """
+    """ Check that a block more than 5 seconds in the future is rejected """
 
     def test_setup_network(self, sandbox: Sandbox):
         sandbox.add_node(1, params=constants.NODE_PARAMS)
@@ -21,7 +21,7 @@ class TestForgeBlock:
 
     def test_activate_proto_demo_time_shifted_ok(self, sandbox: Sandbox):
         parameters = {}  # type: dict
-        delta = datetime.timedelta(seconds=10)
+        delta = datetime.timedelta(seconds=5)
         sandbox.client(1).activate_protocol_json(
             PROTO_DEMO,
             parameters,
diff --git a/tests_python/tests_alpha/test_forge_block.py b/tests_python/tests_alpha/test_forge_block.py
index 1aa64a36b47795418ce77dc446283378ebad2018..babcdeb1d04c0946c00954d4d27a58e11965e649 100755
--- a/tests_python/tests_alpha/test_forge_block.py
+++ b/tests_python/tests_alpha/test_forge_block.py
@@ -9,7 +9,7 @@ PROTO_DEMO = 'ProtoDemoNoopsDemoNoopsDemoNoopsDemoNoopsDemo6XBoYp'
 @pytest.mark.slow
 @pytest.mark.incremental
 class TestForgeBlock:
-    """ Check that a block more than 15 seconds in the future is rejected """
+    """ Check that a block more than 5 seconds in the future is rejected """
 
     def test_setup_network(self, sandbox: Sandbox):
         sandbox.add_node(1, params=constants.NODE_PARAMS)
@@ -21,7 +21,7 @@ class TestForgeBlock:
 
     def test_activate_proto_demo_time_shifted_ok(self, sandbox: Sandbox):
         parameters = {}  # type: dict
-        delta = datetime.timedelta(seconds=10)
+        delta = datetime.timedelta(seconds=5)
         sandbox.client(1).activate_protocol_json(
             PROTO_DEMO,
             parameters,