diff --git a/artiq/firmware/Cargo.lock b/artiq/firmware/Cargo.lock
index 4adc90bc3..3628a5b53 100644
--- a/artiq/firmware/Cargo.lock
+++ b/artiq/firmware/Cargo.lock
@@ -160,7 +160,7 @@ dependencies = [
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "logger_artiq 0.0.0",
  "proto 0.0.0",
- "smoltcp 0.4.0 (git+https://github.com/m-labs/smoltcp?rev=9914616)",
+ "smoltcp 0.4.0 (git+https://github.com/m-labs/smoltcp?rev=30012cc)",
  "std_artiq 0.0.0",
 ]
 
@@ -186,7 +186,7 @@ dependencies = [
 [[package]]
 name = "smoltcp"
 version = "0.4.0"
-source = "git+https://github.com/m-labs/smoltcp?rev=9914616#9914616893c373de3fb52fcd2f06e0fffb4c8904"
+source = "git+https://github.com/m-labs/smoltcp?rev=30012cc#30012cc3b1730f24ced24fc24627b856dc31540b"
 dependencies = [
  "byteorder 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -229,7 +229,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum log_buffer 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ec57723b84bbe7bdf76aa93169c9b59e67473317c6de3a83cb2a0f8ccb2aa493"
 "checksum managed 0.4.0 (git+https://github.com/m-labs/rust-managed.git?rev=629a6786a1cf1692015f464ed16c04eafa5cb8d1)" = "<none>"
 "checksum rustc-cfg 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "56a596b5718bf5e059d59a30af12f7f462a152de147aa462b70892849ee18704"
-"checksum smoltcp 0.4.0 (git+https://github.com/m-labs/smoltcp?rev=9914616)" = "<none>"
+"checksum smoltcp 0.4.0 (git+https://github.com/m-labs/smoltcp?rev=30012cc)" = "<none>"
 "checksum walkdir 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "dd7c16466ecc507c7cb5988db03e6eab4aaeab89a5c37a29251fcfd3ac9b7afe"
 "checksum winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "167dc9d6949a9b857f3451275e911c3f44255842c1f7a76f33c55103a909087a"
 "checksum winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "2d315eee3b34aca4797b2da6b13ed88266e6d612562a0c46390af8299fc699bc"
diff --git a/artiq/firmware/runtime/Cargo.toml b/artiq/firmware/runtime/Cargo.toml
index d376677d7..3ff82710b 100644
--- a/artiq/firmware/runtime/Cargo.toml
+++ b/artiq/firmware/runtime/Cargo.toml
@@ -37,6 +37,6 @@ features = ["alloc"]
 
 [dependencies.smoltcp]
 git = "https://github.com/m-labs/smoltcp"
-rev = "9914616"
+rev = "30012cc"
 default-features = false
 features = ["alloc", "log", "socket-tcp"]