diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8246a9e..1a69295 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,7 +18,7 @@ jobs:
           - stable
           - beta
           - nightly
-          - 1.56.0
+          - 1.51.0
     steps:
       - uses: actions/checkout@v2.3.4
       - uses: actions-rs/toolchain@v1.0.7
diff --git a/Cargo.lock b/Cargo.lock
index bff4274..c0ce8b4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -25,41 +25,47 @@ dependencies = [
 
 [[package]]
 name = "aho-corasick"
-version = "0.7.18"
+version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e37cfd5e7657ada45f742d6e99ca5788580b5c529dc78faf11ece6dc702656f"
+checksum = "58fb5e95d83b38284460a5fda7d6470aa0b8844d283a0b614b8535e880800d2d"
 dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "arc-swap"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e43c468bcaa343ddcad9e46806e066e39f62434898b20f5af21261da910d5c7"
+
 [[package]]
 name = "atty"
-version = "0.2.14"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+checksum = "8352656fd42c30a0c3c89d26dea01e3b77c0ab2af18230835c15e2e13cd51859"
 dependencies = [
- "hermit-abi",
  "libc",
+ "termion",
  "winapi",
 ]
 
 [[package]]
 name = "bitflags"
-version = "1.2.1"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+checksum = "3d155346769a6855b86399e9bc3814ab343cd3d62c7e985113d46a0ec3c281fd"
 
 [[package]]
 name = "bumpalo"
-version = "3.11.1"
+version = "3.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "572f695136211188308f16ad2ca5c851a712c464060ae6974944458eb83880ba"
+checksum = "12ae9db68ad7fac5fe51304d20f016c911539251075a214f8e663babefa35187"
 
 [[package]]
 name = "cfg-if"
-version = "0.1.10"
+version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+checksum = "405216fd8fe65f718daa7102ea808a946b6ce40c742998fbfd3463645552de18"
 
 [[package]]
 name = "cfg-if"
@@ -79,9 +85,9 @@ dependencies = [
 
 [[package]]
 name = "dashmap"
-version = "5.2.0"
+version = "5.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4c8858831f7781322e539ea39e72449c46b059638250c14344fec8d0aa6e539c"
+checksum = "c0834a35a3fce649144119e18da2a4d8ed12ef3862f47183fd46f625d072d96c"
 dependencies = [
  "cfg-if 1.0.0",
  "num_cpus",
@@ -90,15 +96,15 @@ dependencies = [
 
 [[package]]
 name = "document-features"
-version = "0.2.1"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b01c09fd63b5136fba41aa625c7b3254f0aa0a435ff6ec4b2c9a28d496c83c88"
+checksum = "b0145598eea78b706096d9d2c574031ce2fd988daac32f44338a62897bf9e520"
 
 [[package]]
 name = "either"
-version = "1.6.1"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+checksum = "5845bf77d497f79416df39462df26d4a8b71dd6440246848ee63709476dbb9a6"
 
 [[package]]
 name = "env_logger"
@@ -202,24 +208,24 @@ dependencies = [
 
 [[package]]
 name = "hermit-abi"
-version = "0.1.17"
+version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5aca5565f760fb5b220e499d72710ed156fdb74e631659e99377d9ebfbd13ae8"
+checksum = "307c3c9f937f38e3534b1d6447ecf090cafcc9744e4a6360e8b037b2cf5af120"
 dependencies = [
  "libc",
 ]
 
 [[package]]
 name = "humantime"
-version = "2.1.0"
+version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
+checksum = "b9b6c53306532d3c8e8087b44e6580e10db51a023cf9b433cea2ac38066b92da"
 
 [[package]]
 name = "itertools"
-version = "0.10.3"
+version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a9a9d19fa1e79b6215ff29b9d6880b706147f16e9b1dbb1e4e5947b5b02bc5e3"
+checksum = "37d572918e350e82412fe766d24b15e6682fb2ed2bbe018280caa810397cb319"
 dependencies = [
  "either",
 ]
@@ -235,15 +241,15 @@ dependencies = [
 
 [[package]]
 name = "lazy_static"
-version = "1.4.0"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+checksum = "a374c89b9db55895453a74c1e38861d9deec0b01b405a82516e9d5de4820dea1"
 
 [[package]]
 name = "libc"
-version = "0.2.119"
+version = "0.2.114"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1bf2e165bb3457c8e098ea76f3e3bc9db55f87aa90d52d0e6be741470916aaa4"
+checksum = "b0005d08a8f7b65fb8073cb697aa0b12b631ed251ce73d862ce50eeb52ce3b50"
 
 [[package]]
 name = "lock_api"
@@ -256,47 +262,47 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.11"
+version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4fabed175da42fed1fa0746b0ea71f412aa9d35e76e95e59b192c64b9dc2bf8b"
+checksum = "14b6052be84e6b71ab17edffc2eeabf5c2c3ae1fdb464aae35ac50c67a44e1f7"
 dependencies = [
- "cfg-if 0.1.10",
+ "cfg-if 0.1.3",
 ]
 
 [[package]]
 name = "memchr"
-version = "2.5.0"
+version = "2.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+checksum = "88579771288728879b57485cc7d6b07d648c9f0141eb955f8ab7f9d45394468e"
 
 [[package]]
 name = "mio"
-version = "0.8.2"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "52da4364ffb0e4fe33a9841a98a3f3014fb964045ce4f7a45a398243c8d6b0c9"
+checksum = "ba272f85fa0b41fc91872be579b3bbe0f56b792aa361a380eb669469f68dafb2"
 dependencies = [
  "libc",
  "log",
  "miow",
  "ntapi",
- "wasi",
  "winapi",
 ]
 
 [[package]]
 name = "miow"
-version = "0.3.7"
+version = "0.3.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b9f1c5b025cda876f66ef43a113f91ebc9f4ccef34843000e0adf6ebbab84e21"
+checksum = "5a33c1b55807fbed163481b5ba66db4b2fa6cde694a5027be10fb724206c5897"
 dependencies = [
+ "socket2 0.3.17",
  "winapi",
 ]
 
 [[package]]
 name = "ntapi"
-version = "0.3.7"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c28774a7fd2fbb4f0babd8237ce554b73af68021b5f695a3cebd6c59bac0980f"
+checksum = "bcdaac6150484ca8fed0f2ba30c2970d05da1ceac10d1beefae91ff4ada7928f"
 dependencies = [
  "winapi",
 ]
@@ -313,9 +319,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.10.0"
+version = "1.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "87f3e037eac156d1775da914196f0f37741a274155e34a0b7e427c35d2a2ecb9"
+checksum = "13bd41f508810a131401606d54ac32a467c97172d74ba7662562ebba5ad07fa0"
 
 [[package]]
 name = "parking_lot"
@@ -329,22 +335,22 @@ dependencies = [
 
 [[package]]
 name = "parking_lot_core"
-version = "0.9.1"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "28141e0cc4143da2443301914478dc976a61ffdb3f043058310c70df2fed8954"
+checksum = "b2f4f894f3865f6c0e02810fc597300f34dc2510f66400da262d8ae10e75767d"
 dependencies = [
  "cfg-if 1.0.0",
  "libc",
- "redox_syscall",
+ "redox_syscall 0.2.8",
  "smallvec",
  "windows-sys",
 ]
 
 [[package]]
 name = "pin-project-lite"
-version = "0.2.6"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc0e1f259c92177c30a4c9d177246edd0a3568b25756a977d0632cf8fa37e905"
+checksum = "0cf491442e4b033ed1c722cb9f0df5fcfcf4de682466c46469c36bc47dc5548a"
 
 [[package]]
 name = "pin-utils"
@@ -354,47 +360,63 @@ checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.24"
+version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e0704ee1a7e00d7bb417d0770ea303c1bccbabf0ef1667dae92b5967f5f8a71"
+checksum = "51ef7cd2518ead700af67bf9d1a658d90b6037d77110fd9c0445429d0ba1c6c9"
 dependencies = [
  "unicode-xid",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.7"
+version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
+checksum = "2bdc6c187c65bca4260c9011c9e3132efe4909da44726bad24cf7572ae338d7f"
 dependencies = [
  "proc-macro2",
 ]
 
 [[package]]
 name = "redox_syscall"
-version = "0.2.10"
+version = "0.1.38"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0a12d51a5b5fd700e6c757f15877685bfa04fd7eb60c108f01d045cafa0073c2"
+
+[[package]]
+name = "redox_syscall"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8383f39639269cde97d255a32bdb68c047337295414940c68bdd30c2e13203ff"
+checksum = "742739e41cd49414de871ea5e549afb7e2a3ac77b589bcbebe8c82fab37147fc"
 dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "redox_termios"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bc495930de8d330f14856cface52561b7d79a072c76e438cf8f34d7233a35fa7"
+dependencies = [
+ "redox_syscall 0.1.38",
+]
+
 [[package]]
 name = "regex"
-version = "1.5.6"
+version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d83f127d94bdbcda4c8cc2e50f6f84f4b611f69c902699ca385a39c3a75f9ff1"
+checksum = "fc98360d9e6ad383647702acc90f80b0582eac3ea577ab47d96325d3575de908"
 dependencies = [
  "aho-corasick",
  "memchr",
  "regex-syntax",
+ "thread_local",
 ]
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.26"
+version = "0.6.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "49b3de9ec5dc0a3417da371aab17d729997c15010e7fd24ff707773a33bddb64"
+checksum = "11a7e20d1cce64ef2fed88b66d347f88bd9babb82845b2b858f3edbf59a4f716"
 
 [[package]]
 name = "scoped-tls"
@@ -451,24 +473,37 @@ dependencies = [
 
 [[package]]
 name = "signal-hook-registry"
-version = "1.3.0"
+version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "16f1d0fef1604ba8f7a073c7e701f213e056707210e9020af4528e0101ce11a6"
+checksum = "1797d48f38f91643908bb14e35e79928f9f4b3cefb2420a564dde0991b4358dc"
 dependencies = [
+ "arc-swap",
  "libc",
 ]
 
 [[package]]
 name = "slab"
-version = "0.4.6"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eb703cfe953bccee95685111adeedb76fabe4e97549a58d16f03ea7b9367bb32"
+checksum = "c111b5bd5695e56cffe5129854aa230b39c93a305372fdbb2668ca2394eea9f8"
 
 [[package]]
 name = "smallvec"
-version = "1.8.0"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe0f37c9e8f3c5a4a66ad655a93c74daac4ad00c441533bf5c6e7990bb42604e"
+
+[[package]]
+name = "socket2"
+version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2dd574626839106c320a323308629dcb1acfc96e32a8cba364ddc61ac23ee83"
+checksum = "2c29947abdee2a218277abeca306f25789c938e500ea5a9d4b12a5a504466902"
+dependencies = [
+ "cfg-if 1.0.0",
+ "libc",
+ "redox_syscall 0.1.38",
+ "winapi",
+]
 
 [[package]]
 name = "socket2"
@@ -493,11 +528,31 @@ dependencies = [
 
 [[package]]
 name = "termcolor"
-version = "1.1.0"
+version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bb6bfa289a4d7c5766392812c0a1f4c1ba45afa1ad47803c11e1f407d846d75f"
+checksum = "3390f44f1f706d8870297b6a2c4f92d9ab65a37c265fbbc6ac4ee72bcc2f3698"
 dependencies = [
- "winapi-util",
+ "wincolor",
+]
+
+[[package]]
+name = "termion"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8affd752d0f2c7127d6d5f1b98182a5471606b48b1a955165d39eb5e4887ceba"
+dependencies = [
+ "libc",
+ "redox_syscall 0.1.38",
+ "redox_termios",
+]
+
+[[package]]
+name = "thread_local"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6b53e329000edc2b34dbe8545fd20e55a333362d0a321909685a19bd28c3f1b"
+dependencies = [
+ "lazy_static",
 ]
 
 [[package]]
@@ -512,7 +567,7 @@ dependencies = [
  "parking_lot",
  "pin-project-lite",
  "signal-hook-registry",
- "socket2",
+ "socket2 0.4.4",
  "tokio-macros",
  "winapi",
 ]
@@ -530,15 +585,9 @@ dependencies = [
 
 [[package]]
 name = "unicode-xid"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
-
-[[package]]
-name = "wasi"
-version = "0.11.0+wasi-snapshot-preview1"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
 
 [[package]]
 name = "wasm-bindgen"
@@ -632,9 +681,9 @@ dependencies = [
 
 [[package]]
 name = "web-sys"
-version = "0.3.58"
+version = "0.3.36"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2fed94beee57daf8dd7d51f2b15dc2bcde92d7a72304cdf662a4371008b71b90"
+checksum = "721c6263e2c66fd44501cc5efbfa2b7dfa775d13e4ea38c46299646ed1f9c70a"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -656,26 +705,26 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
-[[package]]
-name = "winapi-util"
-version = "0.1.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
-dependencies = [
- "winapi",
-]
-
 [[package]]
 name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
 
+[[package]]
+name = "wincolor"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9dc3aa9dcda98b5a16150c54619c1ead22e3d3a5d458778ae914be760aa981a"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "windows-sys"
-version = "0.32.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3df6e476185f92a12c072be4a189a0210dcdcf512a1891d6dff9edb874deadc6"
+checksum = "ceb069ac8b2117d36924190469735767f0990833935ab430155e71a44bafe148"
 dependencies = [
  "windows_aarch64_msvc",
  "windows_i686_gnu",
@@ -686,30 +735,30 @@ dependencies = [
 
 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.32.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d8e92753b1c443191654ec532f14c199742964a061be25d77d7a96f09db20bf5"
+checksum = "c3d027175d00b01e0cbeb97d6ab6ebe03b12330a35786cbaca5252b1c4bf5d9b"
 
 [[package]]
 name = "windows_i686_gnu"
-version = "0.32.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a711c68811799e017b6038e0922cb27a5e2f43a2ddb609fe0b6f3eeda9de615"
+checksum = "8793f59f7b8e8b01eda1a652b2697d87b93097198ae85f823b969ca5b89bba58"
 
 [[package]]
 name = "windows_i686_msvc"
-version = "0.32.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "146c11bb1a02615db74680b32a68e2d61f553cc24c4eb5b4ca10311740e44172"
+checksum = "8602f6c418b67024be2996c512f5f995de3ba417f4c75af68401ab8756796ae4"
 
 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.32.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c912b12f7454c6620635bbff3450962753834be2a594819bd5e945af18ec64bc"
+checksum = "f3d615f419543e0bd7d2b3323af0d86ff19cbc4f816e6453f36a2c2ce889c354"
 
 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.32.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "504a2476202769977a040c6364301a3f65d0cc9e3fb08600b2bda150a0488316"
+checksum = "11d95421d9ed3672c280884da53201a5c46b7b2765ca6faf34b0d71cf34a3561"
diff --git a/README.md b/README.md
index 3369e54..3eb6848 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 [![Docs](https://docs.rs/serial_test/badge.svg)](https://docs.rs/serial_test/)
 [![MIT license](https://img.shields.io/crates/l/serial_test.svg)](./LICENSE)
 [![Build Status](https://github.com/palfrey/serial_test/workflows/Continuous%20integration/badge.svg?branch=main)](https://github.com/palfrey/serial_test/actions)
-[![MSRV: 1.56.0](https://flat.badgen.net/badge/MSRV/1.56.0/purple)](https://blog.rust-lang.org/2021/10/21/Rust-1.56.0.html)
+[![MSRV: 1.51.0](https://flat.badgen.net/badge/MSRV/1.51.0/purple)](https://blog.rust-lang.org/2021/03/25/Rust-1.51.0.html)
 
 `serial_test` allows for the creation of serialised Rust tests using the `serial` attribute
 e.g.
@@ -34,7 +34,7 @@ similar properties but based off file locking. Note that there are no guarantees
 `file_serial` as they lock using different methods, and `parallel` doesn't support `file_serial` yet (patches welcomed!).
 
 ## Usage
-We require at least Rust 1.56. Upgrades to this will require at least a minor version bump (while in 0.x versions) and a major version bump post-1.0.
+We require at least Rust 1.51. Upgrades to this will require at least a minor version bump (while in 0.x versions) and a major version bump post-1.0.
 
 Add to your Cargo.toml
 ```toml
diff --git a/serial_test_test/Cargo.toml b/serial_test_test/Cargo.toml
index 2396ba0..b01161e 100644
--- a/serial_test_test/Cargo.toml
+++ b/serial_test_test/Cargo.toml
@@ -12,7 +12,7 @@ lazy_static = "^1.2"
 env_logger = "^0.9"
 parking_lot = "^0.12"
 wasm-bindgen-test = {version="0.3.0", optional=true}
-scoped-tls = {version="=1.0.0", optional=true} # Locked down for 1.56 compat
+scoped-tls = {version="=1.0.0", optional=true} # Locked down for 1.51 compat
 
 [dev-dependencies]
 tokio = { version = "^1.17", features = ["macros", "rt"] }