diff --git a/.cargo/config b/.cargo/config
index 2109ab5..3b89a87 100644
--- a/.cargo/config
+++ b/.cargo/config
@@ -3,7 +3,7 @@ rustflags = [
   "-C", "link-arg=-Tlink.x",
   "-C", "target-feature=a9,armv7-a,neon",
   "-C", "target-cpu=cortex-a9",
-  #"-Zcrate-attr=feature(const_fn)"
+  "-Zcrate-attr=feature(const_fn)"
 ]
 
 [build]
diff --git a/Cargo.lock b/Cargo.lock
index ce246a2..64bf593 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -39,7 +39,7 @@ checksum = "3748f82c7d366a0b4950257d19db685d4958d2fa27c6d164a3f069fec42b748b"
 [[package]]
 name = "core_io"
 version = "0.1.20210325"
-source = "git+https://git.m-labs.hk/abdul124/core_io?rev=7b6dba6#7b6dba64ed552e87c67ccbef4bc201c5747434a9"
+source = "git+https://git.m-labs.hk/abdul124/core_io?rev=998b1e9#998b1e99907faf8de0381ea9fa54fe649ce6bfdd"
 dependencies = [
  "rustc_version",
 ]
@@ -70,7 +70,7 @@ dependencies = [
 [[package]]
 name = "fatfs"
 version = "0.3.5"
-source = "git+https://git.m-labs.hk/abdul124/fatfs?rev=9b0d4bd#9b0d4bd28035134d0ae9a41915fbb303a2aeb469"
+source = "git+https://git.m-labs.hk/abdul124/fatfs?rev=05e9feb#05e9feb52c1c4415b27847ac2ed2303682850f97"
 dependencies = [
  "bitflags",
  "byteorder",
diff --git a/flake.nix b/flake.nix
index a7bb9fc..d387985 100644
--- a/flake.nix
+++ b/flake.nix
@@ -117,8 +117,8 @@
         cargoLock = { 
           lockFile = ./Cargo.lock;
           outputHashes = {
-              "core_io-0.1.20210325" = "sha256-JLlEMx9C0pWVae8Vucm7FqMViwUoA2rRbJyYM9r0s8M=";
-              "fatfs-0.3.5" = "sha256-0ta9IgRyi2tG3Xzm2D6WMdGSMMgRvVThyY2W4k60VwM=";
+              "core_io-0.1.20210325" = "sha256-XM7Y7EeItmNQSVaVLZqpRPSyLj6ZMskUvdYxvmuo1ww=";
+              "fatfs-0.3.5" = "sha256-jCRCZ+QNkRPSPtWrod+6UuX2ULPYTWo77aLegco8Rxg=";
             };
         };
 
diff --git a/libconfig/Cargo.toml b/libconfig/Cargo.toml
index d86ca87..eb418fd 100644
--- a/libconfig/Cargo.toml
+++ b/libconfig/Cargo.toml
@@ -6,8 +6,8 @@ edition = "2018"
 
 [dependencies]
 libboard_zynq = { path = "../libboard_zynq" }
-core_io = { git = "https://git.m-labs.hk/abdul124/core_io.git", rev = "7b6dba6", features = ["collections"] }
-fatfs = { git = "https://git.m-labs.hk/abdul124/fatfs.git", rev = "9b0d4bd", features = ["core_io"], default-features = false }
+core_io = { git = "https://git.m-labs.hk/abdul124/core_io.git", rev = "998b1e9", features = ["collections"] }
+fatfs = { git = "https://git.m-labs.hk/abdul124/fatfs.git", rev = "05e9feb", features = ["core_io"], default-features = false }
 log = "0.4"
 
 [features]
diff --git a/libcortex_a9/src/lib.rs b/libcortex_a9/src/lib.rs
index 2f341d3..467fdbf 100644
--- a/libcortex_a9/src/lib.rs
+++ b/libcortex_a9/src/lib.rs
@@ -1,7 +1,6 @@
 #![no_std]
 #![feature(llvm_asm, global_asm)]
 #![feature(never_type)]
-#![feature(const_fn)]
 
 extern crate alloc;
 
diff --git a/szl/Cargo.toml b/szl/Cargo.toml
index 3c37fdf..3b57e38 100644
--- a/szl/Cargo.toml
+++ b/szl/Cargo.toml
@@ -15,7 +15,7 @@ default = ["target_zc706"]
 [dependencies]
 log = "0.4"
 byteorder = { version = "1.3", default-features = false }
-core_io = { git = "https://git.m-labs.hk/abdul124/core_io.git", rev = "7b6dba6", features = ["collections"] }
+core_io = { git = "https://git.m-labs.hk/abdul124/core_io.git", rev = "998b1e9", features = ["collections"] }
 
 libboard_zynq = { path = "../libboard_zynq" }
 libsupport_zynq = { path = "../libsupport_zynq" }