diff --git a/Cargo.lock b/Cargo.lock
index 35e22d0..48b4f92 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,20 +4,17 @@ version = 3
 
 [[package]]
 name = "a2"
-version = "0.6.2"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b411d99f057bb20c324c758aeab7a063552511b90458d8109b5a6f2df700a8f"
+checksum = "da60b150c4846f18f007bbdf912cefe83aaa88fe6725b8bfc3529e5fd3caa895"
 dependencies = [
- "base64 0.13.1",
+ "base64 0.20.0",
  "erased-serde",
- "futures",
  "http",
  "hyper",
  "hyper-alpn",
- "log",
  "openssl",
  "serde",
- "serde_derive",
  "serde_json",
  "thiserror",
 ]
@@ -254,7 +251,7 @@ dependencies = [
  "futures-lite",
  "rustix",
  "signal-hook",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -393,6 +390,18 @@ version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9e1b586273c5702936fe7b7d6896644d8be71e6314cfe09d3167c95f712589e8"
 
+[[package]]
+name = "base64"
+version = "0.20.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ea22880d78093b0cbe17c89f64a7d457941e65759157ec6cb31a31d652b05e5"
+
+[[package]]
+name = "base64"
+version = "0.21.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
+
 [[package]]
 name = "bincode"
 version = "1.3.3"
@@ -504,7 +513,7 @@ dependencies = [
  "num-traits",
  "serde",
  "wasm-bindgen",
- "windows-targets",
+ "windows-targets 0.48.5",
 ]
 
 [[package]]
@@ -682,7 +691,7 @@ checksum = "136526188508e25c6fef639d7927dfb3e0e3084488bf202267829cf7fc23dbdd"
 dependencies = [
  "errno-dragonfly",
  "libc",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -766,21 +775,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "futures"
-version = "0.3.28"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "23342abe12aba583913b2e62f22225ff9c950774065e4bfb61a19cd9770fec40"
-dependencies = [
- "futures-channel",
- "futures-core",
- "futures-executor",
- "futures-io",
- "futures-sink",
- "futures-task",
- "futures-util",
-]
-
 [[package]]
 name = "futures-channel"
 version = "0.3.28"
@@ -788,7 +782,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "955518d47e09b25bbebc7a18df10b81f0c766eaf4c4f1cccef2fca5f2a4fb5f2"
 dependencies = [
  "futures-core",
- "futures-sink",
 ]
 
 [[package]]
@@ -797,17 +790,6 @@ version = "0.3.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4bca583b7e26f571124fe5b7561d49cb2868d79116cfa0eefce955557c6fee8c"
 
-[[package]]
-name = "futures-executor"
-version = "0.3.28"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ccecee823288125bd88b4d7f565c9e58e41858e47ab72e8ea2d64e93624386e0"
-dependencies = [
- "futures-core",
- "futures-task",
- "futures-util",
-]
-
 [[package]]
 name = "futures-io"
 version = "0.3.28"
@@ -858,13 +840,9 @@ version = "0.3.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "26b01e40b772d54cf6c6d721c1d1abd0647a0106a12ecaa1c186273392a69533"
 dependencies = [
- "futures-channel",
  "futures-core",
- "futures-io",
  "futures-macro",
- "futures-sink",
  "futures-task",
- "memchr",
  "pin-project-lite 0.2.13",
  "pin-utils",
  "slab",
@@ -1118,17 +1096,16 @@ dependencies = [
 
 [[package]]
 name = "hyper-alpn"
-version = "0.3.0"
+version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "54b255c8c5fd5d0c6396b50cdacbde3b19809a1166023c1b51dc2f86db5d2da9"
+checksum = "bafa0c8f13da51d474d0c0933c7abe8c50e5f8c7ad72ea34ba998104d9190760"
 dependencies = [
- "futures",
  "hyper",
  "log",
  "rustls",
+ "rustls-pemfile",
  "tokio",
  "tokio-rustls",
- "webpki",
  "webpki-roots",
 ]
 
@@ -1198,7 +1175,7 @@ checksum = "eae7b9aee968036d54dce06cebaefd919e4472e753296daccd6d344e3e2df0c2"
 dependencies = [
  "hermit-abi 0.3.2",
  "libc",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1295,7 +1272,7 @@ checksum = "927a765cd3fc26206e66b296465fa9d3e5ab003e651c1b3c060e7956d96b19d2"
 dependencies = [
  "libc",
  "wasi 0.11.0+wasi-snapshot-preview1",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1487,7 +1464,7 @@ dependencies = [
  "libc",
  "log",
  "pin-project-lite 0.2.13",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1644,12 +1621,27 @@ dependencies = [
  "cc",
  "libc",
  "once_cell",
- "spin",
- "untrusted",
+ "spin 0.5.2",
+ "untrusted 0.7.1",
  "web-sys",
  "winapi",
 ]
 
+[[package]]
+name = "ring"
+version = "0.17.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c17fa4cb658e3583423e915b9f3acc01cceaee1860e33d59ebae66adc3a2dc0d"
+dependencies = [
+ "cc",
+ "cfg-if 1.0.0",
+ "getrandom 0.2.10",
+ "libc",
+ "spin 0.9.8",
+ "untrusted 0.9.0",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "route-recognizer"
 version = "0.2.0"
@@ -1682,22 +1674,30 @@ dependencies = [
  "io-lifetimes",
  "libc",
  "linux-raw-sys",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
 name = "rustls"
-version = "0.19.1"
+version = "0.20.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "35edb675feee39aec9c99fa5ff985081995a06d594114ae14cbe797ad7b7a6d7"
+checksum = "1b80e3dec595989ea8510028f30c408a4630db12c9cbb8de34203b89d6577e99"
 dependencies = [
- "base64 0.13.1",
  "log",
- "ring",
+ "ring 0.16.20",
  "sct",
  "webpki",
 ]
 
+[[package]]
+name = "rustls-pemfile"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c74cae0a4cf6ccbbf5f359f08efdf8ee7e1dc532573bf0db71968cb56b1448c"
+dependencies = [
+ "base64 0.21.7",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.15"
@@ -1712,12 +1712,12 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "sct"
-version = "0.6.1"
+version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b362b83898e0e69f38515b82ee15aa80636befe47c3b6d3d89a911e78fc228ce"
+checksum = "da046153aa2352493d6cb7da4b6e5c0c057d8a1d0a9aa8560baffdd945acd414"
 dependencies = [
- "ring",
- "untrusted",
+ "ring 0.17.8",
+ "untrusted 0.9.0",
 ]
 
 [[package]]
@@ -1902,7 +1902,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4031e820eb552adee9295814c0ced9e5cf38ddf1e8b7d566d6de8e2538ea989e"
 dependencies = [
  "libc",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1911,6 +1911,12 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
+[[package]]
+name = "spin"
+version = "0.9.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
+
 [[package]]
 name = "standback"
 version = "0.2.17"
@@ -2213,14 +2219,14 @@ dependencies = [
  "num_cpus",
  "pin-project-lite 0.2.13",
  "socket2 0.5.4",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
 name = "tokio-rustls"
-version = "0.22.0"
+version = "0.23.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc6844de72e57df1980054b38be3a9f4702aba4858be64dd700181a8a6d0e1b6"
+checksum = "c43ee83903113e03984cb9e5cebe6c04a5116269e900e3ddba8f068a62adda59"
 dependencies = [
  "rustls",
  "tokio",
@@ -2328,6 +2334,12 @@ version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a156c684c91ea7d62626509bce3cb4e1d9ed5c4d978f7b4352658f96a4c26b4a"
 
+[[package]]
+name = "untrusted"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ecb6da28b8a351d773b68d5825ac39017e680750f980f3a1a85cd8dd28a47c1"
+
 [[package]]
 name = "url"
 version = "2.4.1"
@@ -2501,19 +2513,19 @@ dependencies = [
 
 [[package]]
 name = "webpki"
-version = "0.21.4"
+version = "0.22.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b8e38c0608262c46d4a56202ebabdeb094cef7e560ca7a226c6bf055188aa4ea"
+checksum = "ed63aea5ce73d0ff405984102c42de94fc55a6b75765d621c65262469b3c9b53"
 dependencies = [
- "ring",
- "untrusted",
+ "ring 0.17.8",
+ "untrusted 0.9.0",
 ]
 
 [[package]]
 name = "webpki-roots"
-version = "0.21.1"
+version = "0.22.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aabe153544e473b775453675851ecc86863d2a81d786d741f6b76778f2a48940"
+checksum = "b6c71e40d7d2c34a5106301fb632274ca37242cd0c9d3e64dbece371a40a2d87"
 dependencies = [
  "webpki",
 ]
@@ -2546,7 +2558,7 @@ version = "0.48.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e686886bc078bc1b0b600cac0147aadb815089b6e4da64016cbd754b6342700f"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.48.5",
 ]
 
 [[package]]
@@ -2555,7 +2567,16 @@ version = "0.48.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "677d2418bec65e3338edb076e806bc1ec15693c5d0104683f2efe857f61056a9"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.48.5",
+]
+
+[[package]]
+name = "windows-sys"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "282be5f36a8ce781fad8c8ae18fa3f9beff57ec1b52cb3de0789201425d9a33d"
+dependencies = [
+ "windows-targets 0.52.3",
 ]
 
 [[package]]
@@ -2564,13 +2585,28 @@ version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a2fa6e2155d7247be68c096456083145c183cbbbc2764150dda45a87197940c"
 dependencies = [
- "windows_aarch64_gnullvm",
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
+ "windows_aarch64_gnullvm 0.48.5",
+ "windows_aarch64_msvc 0.48.5",
+ "windows_i686_gnu 0.48.5",
+ "windows_i686_msvc 0.48.5",
+ "windows_x86_64_gnu 0.48.5",
+ "windows_x86_64_gnullvm 0.48.5",
+ "windows_x86_64_msvc 0.48.5",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d380ba1dc7187569a8a9e91ed34b8ccfc33123bbacb8c0aed2d1ad7f3ef2dc5f"
+dependencies = [
+ "windows_aarch64_gnullvm 0.52.3",
+ "windows_aarch64_msvc 0.52.3",
+ "windows_i686_gnu 0.52.3",
+ "windows_i686_msvc 0.52.3",
+ "windows_x86_64_gnu 0.52.3",
+ "windows_x86_64_gnullvm 0.52.3",
+ "windows_x86_64_msvc 0.52.3",
 ]
 
 [[package]]
@@ -2579,38 +2615,80 @@ version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2b38e32f0abccf9987a4e3079dfb67dcd799fb61361e53e2882c3cbaf0d905d8"
 
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68e5dcfb9413f53afd9c8f86e56a7b4d86d9a2fa26090ea2dc9e40fba56c6ec6"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc35310971f3b2dbbf3f0690a219f40e2d9afcf64f9ab7cc1be722937c26b4bc"
 
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8dab469ebbc45798319e69eebf92308e541ce46760b49b18c6b3fe5e8965b30f"
+
 [[package]]
 name = "windows_i686_gnu"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a75915e7def60c94dcef72200b9a8e58e5091744960da64ec734a6c6e9b3743e"
 
+[[package]]
+name = "windows_i686_gnu"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a4e9b6a7cac734a8b4138a4e1044eac3404d8326b6c0f939276560687a033fb"
+
 [[package]]
 name = "windows_i686_msvc"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f55c233f70c4b27f66c523580f78f1004e8b5a8b659e05a4eb49d4166cca406"
 
+[[package]]
+name = "windows_i686_msvc"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28b0ec9c422ca95ff34a78755cfa6ad4a51371da2a5ace67500cf7ca5f232c58"
+
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
 
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "704131571ba93e89d7cd43482277d6632589b18ecf4468f591fbae0a8b101614"
+
 [[package]]
 name = "windows_x86_64_gnullvm"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
 
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42079295511643151e98d61c38c0acc444e52dd42ab456f7ccfd5152e8ecf21c"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.52.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0770833d60a970638e989b3fa9fd2bb1aaadcf88963d1659fd7d9990196ed2d6"
diff --git a/Cargo.toml b/Cargo.toml
index 0243032..23f77c3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,7 +7,7 @@ license = "MIT OR Apache-2.0"
 
 [dependencies]
 async-std = { version = "1.9", features = ["tokio1", "attributes", "unstable"] }
-a2 = "0.6"
+a2 = "0.8"
 sled = "0.34.2"
 structopt = "0.3.15"
 tide = "0.16.0"
diff --git a/src/notifier.rs b/src/notifier.rs
index 2c25f8e..8c20066 100644
--- a/src/notifier.rs
+++ b/src/notifier.rs
@@ -1,6 +1,6 @@
 use a2::{
-    Client, Endpoint, Error::ResponseError, NotificationBuilder, NotificationOptions, Priority,
-    SilentNotificationBuilder,
+    Client, DefaultNotificationBuilder, Endpoint, Error::ResponseError, NotificationBuilder,
+    NotificationOptions, Priority,
 };
 use anyhow::Result;
 use async_std::prelude::*;
@@ -46,14 +46,23 @@ async fn wakeup(db: &sled::Db, client: &Client, topic: Option<&str>) {
     for device_token in tokens {
         info!("notify: {}", device_token);
 
-        let payload = SilentNotificationBuilder::new().build(
-            &device_token,
-            NotificationOptions {
-                apns_priority: Some(Priority::Normal),
-                apns_topic: topic,
-                ..Default::default()
-            },
-        );
+        // Sent silent notification.
+        // According to <https://developer.apple.com/documentation/usernotifications/generating-a-remote-notification>
+        // to send a silent notification you need to set background notification flag `content-available` to 1
+        // and don't include `alert`, `badge` or `sound`.
+        let payload = DefaultNotificationBuilder::new()
+            .set_content_available()
+            .build(
+                &device_token,
+                NotificationOptions {
+                    // Normal priority (5) means
+                    // "send the notification based on power considerations on the user’s device".
+                    // <https://developer.apple.com/documentation/usernotifications/sending-notification-requests-to-apns>
+                    apns_priority: Some(Priority::Normal),
+                    apns_topic: topic,
+                    ..Default::default()
+                },
+            );
 
         match client.send(payload).await {
             Ok(res) => match res.code {