diff --git a/artiq/firmware/Cargo.lock b/artiq/firmware/Cargo.lock
index 044d1ff8f..ed834b273 100644
--- a/artiq/firmware/Cargo.lock
+++ b/artiq/firmware/Cargo.lock
@@ -29,7 +29,7 @@ dependencies = [
  "build_misoc 0.0.0",
  "byteorder 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "cc 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.0 (git+https://github.com/m-labs/compiler-builtins?rev=1c765ad)",
+ "compiler_builtins 0.1.0 (git+https://github.com/m-labs/compiler-builtins?rev=ca06a5e)",
  "smoltcp 0.4.0 (git+https://github.com/m-labs/smoltcp?rev=181083f)",
 ]
 
@@ -89,7 +89,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "compiler_builtins"
 version = "0.1.0"
-source = "git+https://github.com/m-labs/compiler-builtins?rev=1c765ad#1c765adbe8e246e01db39aba0a71a6b5721e2465"
+source = "git+https://github.com/m-labs/compiler-builtins?rev=ca06a5e#ca06a5e3d5ff9a17210f22401fdf6325f632c59e"
 
 [[package]]
 name = "crc"
@@ -286,7 +286,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum byteorder 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "652805b7e73fada9d85e9a6682a4abd490cb52d96aeecc12e33a0de34dfd0d23"
 "checksum cc 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a9b13a57efd6b30ecd6598ebdb302cca617930b5470647570468a65d12ef9719"
 "checksum cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d4c819a1287eb618df47cc647173c5c4c66ba19d888a6e50d605672aed3140de"
-"checksum compiler_builtins 0.1.0 (git+https://github.com/m-labs/compiler-builtins?rev=1c765ad)" = "<none>"
+"checksum compiler_builtins 0.1.0 (git+https://github.com/m-labs/compiler-builtins?rev=ca06a5e)" = "<none>"
 "checksum crc 1.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bd5d02c0aac6bd68393ed69e00bbc2457f3e89075c6349db7189618dc4ddc1d7"
 "checksum cslice 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0f8cb7306107e4b10e64994de6d3274bd08996a7c1322a27b86482392f96be0a"
 "checksum fringe 1.1.0 (git+https://github.com/m-labs/libfringe?rev=bd23494)" = "<none>"
diff --git a/artiq/firmware/libboard/Cargo.toml b/artiq/firmware/libboard/Cargo.toml
index f00a23abc..c47f8eecb 100644
--- a/artiq/firmware/libboard/Cargo.toml
+++ b/artiq/firmware/libboard/Cargo.toml
@@ -17,7 +17,7 @@ byteorder = { version = "1.0", default-features = false }
 
 [dependencies.compiler_builtins]
 git = "https://github.com/m-labs/compiler-builtins"
-rev = "1c765ad"
+rev = "ca06a5e"
 features = ["mem"]
 
 [dependencies.smoltcp]