diff --git a/Cargo.lock b/Cargo.lock
index 2b715a989d..e3b4b310f7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -29,7 +29,7 @@ dependencies = [
  "log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.83 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_json 1.0.33 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_json 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "standalone-syn 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -176,7 +176,7 @@ dependencies = [
 name = "ralloc_shim"
 version = "0.1.1"
 dependencies = [
- "redox_syscall 0.1.49 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.50 (registry+https://github.com/rust-lang/crates.io-index)",
  "sc 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -213,7 +213,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "redox_syscall"
-version = "0.1.49"
+version = "0.1.50"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -221,7 +221,7 @@ name = "redox_termios"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "redox_syscall 0.1.49 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.50 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -236,7 +236,7 @@ dependencies = [
  "posix-regex 0.1.0",
  "ralloc 1.0.0",
  "rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.49 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.50 (registry+https://github.com/rust-lang/crates.io-index)",
  "sc 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "spin 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "va_list 0.1.0",
@@ -302,7 +302,7 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.33"
+version = "1.0.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "itoa 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -371,7 +371,7 @@ version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "libc 0.2.45 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.49 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.50 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -472,7 +472,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)" = "e464cd887e869cddcae8792a4ee31d23c7edd516700695608f5b98c67ee0131c"
 "checksum rand_core 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1961a422c4d189dfb50ffa9320bf1f2a9bd54ecb92792fb9477f99a1045f3372"
 "checksum rand_core 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0905b6b7079ec73b314d4c748701f6931eb79fd97c668caa3f1899b22b32c6db"
-"checksum redox_syscall 0.1.49 (registry+https://github.com/rust-lang/crates.io-index)" = "f22c50afdcf3f0a31ebb6b47697f6a7c5e5a24967e842858118bce0615f0afad"
+"checksum redox_syscall 0.1.50 (registry+https://github.com/rust-lang/crates.io-index)" = "52ee9a534dc1301776eff45b4fa92d2c39b1d8c3d3357e6eb593e0d795506fc2"
 "checksum redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7e891cfe48e9100a70a3b6eb652fef28920c117d366339687bd5576160db0f76"
 "checksum remove_dir_all 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3488ba1b9a2084d38645c4c08276a1752dcbf2c7130d74f1569681ad5d2799c5"
 "checksum rustc_version 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)" = "c5f5376ea5e30ce23c03eb77cbe4962b988deead10910c372b226388b594c084"
@@ -482,7 +482,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum serde 1.0.83 (registry+https://github.com/rust-lang/crates.io-index)" = "157e12af46859e968da75dea9845530e13d03bcab2009a41b9b7bb3cf4eb3ec2"
 "checksum serde_derive 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)" = "652bc323d694dc925829725ec6c890156d8e70ae5202919869cb00fe2eff3788"
 "checksum serde_derive_internals 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)" = "32f1926285523b2db55df263d2aa4eb69ddcfa7a7eade6430323637866b513ab"
-"checksum serde_json 1.0.33 (registry+https://github.com/rust-lang/crates.io-index)" = "c37ccd6be3ed1fdf419ee848f7c758eb31b054d7cd3ae3600e3bae0adf569811"
+"checksum serde_json 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)" = "bdf540260cfee6da923831f4776ddc495ada940c30117977c70f1313a6130545"
 "checksum spin 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)" = "ceac490aa12c567115b40b7b7fceca03a6c9d53d5defea066123debc83c5dc1f"
 "checksum standalone-quote 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)" = "dcedac1d6d98e7e9d1d6e628f5635af9566688ae5f6cea70a3976f495ae8d839"
 "checksum standalone-syn 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)" = "115808f5187c07c23cb93eee49d542fae54c6e8285d3a24c6ff683fcde9243db"
diff --git a/src/header/sys_mman/mod.rs b/src/header/sys_mman/mod.rs
index 9ff48c1faa..4ecb3fe68a 100644
--- a/src/header/sys_mman/mod.rs
+++ b/src/header/sys_mman/mod.rs
@@ -33,9 +33,9 @@ pub unsafe extern "C" fn mmap(
     Sys::mmap(addr, len, prot, flags, fildes, off)
 }
 
-// #[no_mangle]
-pub extern "C" fn mprotect(addr: *mut c_void, len: usize, prot: c_int) -> c_int {
-    unimplemented!();
+#[no_mangle]
+pub unsafe extern "C" fn mprotect(addr: *mut c_void, len: usize, prot: c_int) -> c_int {
+    Sys::mprotect(addr, len, prot)
 }
 
 // #[no_mangle]
diff --git a/src/platform/linux/mod.rs b/src/platform/linux/mod.rs
index f6c13b9cd3..5268bf60cb 100644
--- a/src/platform/linux/mod.rs
+++ b/src/platform/linux/mod.rs
@@ -298,6 +298,10 @@ impl Pal for Sys {
         e(syscall!(MMAP, addr, len, prot, flags, fildes, off)) as *mut c_void
     }
 
+    unsafe fn mprotect(addr: *mut c_void, len: usize, prot: c_int) -> c_int {
+        e(syscall!(MPROTECT, addr, len, prot)) as c_int
+    }
+
     unsafe fn munmap(addr: *mut c_void, len: usize) -> c_int {
         e(syscall!(MUNMAP, addr, len)) as c_int
     }
diff --git a/src/platform/pal/mod.rs b/src/platform/pal/mod.rs
index b85bf0ed87..79d5217370 100644
--- a/src/platform/pal/mod.rs
+++ b/src/platform/pal/mod.rs
@@ -106,6 +106,8 @@ pub trait Pal {
         off: off_t,
     ) -> *mut c_void;
 
+    unsafe fn mprotect(addr: *mut c_void, len: usize, prot: c_int) -> c_int;
+
     unsafe fn munmap(addr: *mut c_void, len: usize) -> c_int;
 
     fn nanosleep(rqtp: *const timespec, rmtp: *mut timespec) -> c_int;
diff --git a/src/platform/redox/mod.rs b/src/platform/redox/mod.rs
index e39503b053..318745cbb5 100644
--- a/src/platform/redox/mod.rs
+++ b/src/platform/redox/mod.rs
@@ -642,6 +642,10 @@ impl Pal for Sys {
         }
     }
 
+    unsafe fn mprotect(addr: *mut c_void, len: usize, prot: c_int) -> c_int {
+        e(syscall::mprotect(addr as usize, len, (prot as usize) << 16)) as c_int
+    }
+
     unsafe fn munmap(addr: *mut c_void, _len: usize) -> c_int {
         if e(syscall::funmap(addr as usize)) == !0 {
             return !0;