diff --git a/os/src/server/part_blk/main.cc b/os/src/server/part_blk/main.cc
index b6a589b9a..f644a3a18 100644
--- a/os/src/server/part_blk/main.cc
+++ b/os/src/server/part_blk/main.cc
@@ -42,7 +42,7 @@ int main()
 		return 1;
 	}
 
-	enum { STACK_SIZE = 512 * sizeof(Genode::size_t) };
+	enum { STACK_SIZE = 1024 * sizeof(Genode::size_t) };
 	static Cap_connection cap;
 	static Rpc_entrypoint ep(&cap, STACK_SIZE, "part_ep");
 	static Block::Root block_root(&ep, env()->heap(), receiver);
diff --git a/os/src/test/blk/cli/main.cc b/os/src/test/blk/cli/main.cc
index 1a1882178..8d1ae6292 100644
--- a/os/src/test/blk/cli/main.cc
+++ b/os/src/test/blk/cli/main.cc
@@ -69,7 +69,8 @@ class Test
 		{
 			return bulk +
 			       sizeof(Block::Session::Tx_policy::Ack_queue) +
-			       sizeof(Block::Session::Tx_policy::Submit_queue);
+			       sizeof(Block::Session::Tx_policy::Submit_queue) +
+			       (1 << Block::Packet_descriptor::PACKET_ALIGNMENT) - 1;
 		}
 
 		void _ack_avail(unsigned)       { ack_avail();     }