diff --git a/wasmtime-wasi-c/Cargo.toml b/wasmtime-wasi-c/Cargo.toml
index 9952b4942c..3f9683d132 100644
--- a/wasmtime-wasi-c/Cargo.toml
+++ b/wasmtime-wasi-c/Cargo.toml
@@ -17,7 +17,6 @@ cranelift-codegen = "0.30.0"
 cranelift-entity = "0.30.0"
 cranelift-wasm = "0.30.0"
 target-lexicon = "0.3.0"
-cast = { version = "0.2.2", default-features = false }
 log = { version = "0.4.6", default-features = false }
 libc = "0.2.50"
 
diff --git a/wasmtime-wasi-c/src/lib.rs b/wasmtime-wasi-c/src/lib.rs
index 712ee83b9c..6a4b3b769b 100644
--- a/wasmtime-wasi-c/src/lib.rs
+++ b/wasmtime-wasi-c/src/lib.rs
@@ -1,4 +1,3 @@
-extern crate cast;
 extern crate cranelift_codegen;
 extern crate cranelift_entity;
 extern crate cranelift_wasm;
diff --git a/wasmtime-wasi-c/src/syscalls.rs b/wasmtime-wasi-c/src/syscalls.rs
index 687e1a6f76..ab2642fcca 100644
--- a/wasmtime-wasi-c/src/syscalls.rs
+++ b/wasmtime-wasi-c/src/syscalls.rs
@@ -2,6 +2,7 @@ use crate::host::{argv_environ_values, fd_prestats, fd_table};
 use crate::instantiate::WASIState;
 use cranelift_codegen::ir::types::{Type, I32, I64};
 use host;
+use std::convert::TryFrom;
 use std::{mem, ptr, slice, str};
 use translate::*;
 use wasm32;
@@ -170,11 +171,11 @@ syscalls! {
 
         let vmctx = &mut *vmctx;
         let argv_environ = get_argv_environ(vmctx);
-        let argc = match cast::u32((*argv_environ).argc) {
+        let argc = match u32::try_from((*argv_environ).argc) {
             Ok(argc) => argc,
             Err(_) => return wasm32::__WASI_ENOMEM,
         };
-        let argv_buf_size = match cast::u32((*argv_environ).argv_buf_size) {
+        let argv_buf_size = match u32::try_from((*argv_environ).argv_buf_size) {
             Ok(argc) => argc,
             Err(_) => return wasm32::__WASI_ENOMEM,
         };
@@ -307,11 +308,11 @@ syscalls! {
 
         let vmctx = &mut *vmctx;
         let argv_environ = get_argv_environ(vmctx);
-        let environ_count = match cast::u32((*argv_environ).environ_count) {
+        let environ_count = match u32::try_from((*argv_environ).environ_count) {
             Ok(host_environ_count) => host_environ_count,
             Err(_) => return wasm32::__WASI_ENOMEM,
         };
-        let environ_buf_size = match cast::u32((*argv_environ).environ_buf_size) {
+        let environ_buf_size = match u32::try_from((*argv_environ).environ_buf_size) {
             Ok(host_environ_buf_size) => host_environ_buf_size,
             Err(_) => return wasm32::__WASI_ENOMEM,
         };
diff --git a/wasmtime-wasi-c/src/translate.rs b/wasmtime-wasi-c/src/translate.rs
index 2eb0c811da..752e0f73ff 100644
--- a/wasmtime-wasi-c/src/translate.rs
+++ b/wasmtime-wasi-c/src/translate.rs
@@ -1,6 +1,5 @@
-use cast;
-use cast::From as _0;
 use host;
+use std::convert::TryFrom;
 use std::mem::{align_of, size_of, zeroed};
 use std::slice;
 use wasm32;
@@ -85,7 +84,7 @@ pub unsafe fn decode_slice_of<T>(
     ptr: wasm32::uintptr_t,
     len: wasm32::size_t,
 ) -> Result<(*mut T, usize), host::__wasi_errno_t> {
-    let len = cast::usize(len);
+    let len = usize::try_from(len).unwrap();
 
     let ptr = decode_ptr(
         vmctx,
@@ -98,7 +97,7 @@ pub unsafe fn decode_slice_of<T>(
 }
 
 pub fn encode_usize(len: usize) -> wasm32::size_t {
-    cast::u32(len).unwrap()
+    u32::try_from(len).unwrap()
 }
 
 pub fn encode_device(device: host::__wasi_device_t) -> wasm32::__wasi_device_t {
@@ -274,7 +273,7 @@ pub unsafe fn decode_ciovec(
     vmctx: &mut VMContext,
     ciovec: &wasm32::__wasi_ciovec_t,
 ) -> Result<host::__wasi_ciovec_t, host::__wasi_errno_t> {
-    let len = cast::usize(ciovec.buf_len);
+    let len = usize::try_from(ciovec.buf_len).unwrap();
     Ok(host::__wasi_ciovec_t {
         buf: decode_ptr(vmctx, ciovec.buf, len, 1)? as *const host::void,
         buf_len: len,
@@ -285,7 +284,7 @@ pub unsafe fn decode_iovec(
     vmctx: &mut VMContext,
     iovec: &wasm32::__wasi_iovec_t,
 ) -> Result<host::__wasi_iovec_t, host::__wasi_errno_t> {
-    let len = cast::usize(iovec.buf_len);
+    let len = usize::try_from(iovec.buf_len).unwrap();
     Ok(host::__wasi_iovec_t {
         buf: decode_ptr(vmctx, iovec.buf, len, 1)? as *mut host::void,
         buf_len: len,
@@ -416,7 +415,7 @@ pub unsafe fn encode_fd_byref(
     fd_ptr: wasm32::uintptr_t,
     fd: host::__wasi_fd_t,
 ) {
-    encode_pointee::<wasm32::__wasi_fd_t>(vmctx, fd_ptr, wasm32::size_t::cast(fd))
+    encode_pointee::<wasm32::__wasi_fd_t>(vmctx, fd_ptr, wasm32::size_t::try_from(fd).unwrap())
 }
 
 pub unsafe fn decode_timestamp_byref(
@@ -434,7 +433,7 @@ pub unsafe fn encode_timestamp_byref(
     encode_pointee::<wasm32::__wasi_timestamp_t>(
         vmctx,
         timestamp_ptr,
-        wasm32::__wasi_timestamp_t::cast(host_timestamp),
+        wasm32::__wasi_timestamp_t::try_from(host_timestamp).unwrap(),
     )
 }
 
@@ -453,7 +452,7 @@ pub unsafe fn encode_filesize_byref(
     encode_pointee::<wasm32::__wasi_filesize_t>(
         vmctx,
         filesize_ptr,
-        wasm32::__wasi_filesize_t::cast(host_filesize),
+        wasm32::__wasi_filesize_t::try_from(host_filesize).unwrap(),
     )
 }
 
@@ -472,7 +471,7 @@ pub unsafe fn encode_roflags_byref(
     encode_pointee::<wasm32::__wasi_roflags_t>(
         vmctx,
         roflags_ptr,
-        wasm32::__wasi_roflags_t::cast(host_roflags),
+        wasm32::__wasi_roflags_t::try_from(host_roflags).unwrap(),
     )
 }
 
@@ -488,7 +487,11 @@ pub unsafe fn encode_usize_byref(
     usize_ptr: wasm32::uintptr_t,
     host_usize: usize,
 ) {
-    encode_pointee::<wasm32::size_t>(vmctx, usize_ptr, wasm32::size_t::cast(host_usize).unwrap())
+    encode_pointee::<wasm32::size_t>(
+        vmctx,
+        usize_ptr,
+        wasm32::size_t::try_from(host_usize).unwrap(),
+    )
 }
 
 pub unsafe fn decode_prestat_byref(