diff --git a/Cargo.lock b/Cargo.lock
index 69d526c6f6..0a3d8e388b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1162,7 +1162,7 @@ checksum = "1d428afc93ad288f6dffc1fa5f4a78201ad2eec33c5a522e51c181009eb09061"
 dependencies = [
  "byteorder",
  "dynasm",
- "memmap2 0.5.0",
+ "memmap2 0.5.3",
 ]
 
 [[package]]
@@ -2018,9 +2018,9 @@ dependencies = [
 
 [[package]]
 name = "memmap2"
-version = "0.5.0"
+version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4647a11b578fead29cdbb34d4adef8dd3dc35b876c9c6d5240d83f205abfe96e"
+checksum = "057a3db23999c867821a7a59feb06a578fcb03685e983dff90daf9e7d24ac08f"
 dependencies = [
  "libc",
 ]
@@ -3195,8 +3195,10 @@ dependencies = [
  "roc_target",
  "roc_types",
  "roc_unify",
+ "slab",
  "snafu",
  "ven_graph",
+ "winapi",
 ]
 
 [[package]]
@@ -3495,7 +3497,7 @@ dependencies = [
  "bumpalo",
  "clap 3.0.0-beta.5",
  "iced-x86",
- "memmap2 0.5.0",
+ "memmap2 0.5.3",
  "object 0.26.2",
  "roc_build",
  "roc_collections",
@@ -3825,7 +3827,7 @@ checksum = "61b3909d758bb75c79f23d4736fac9433868679d3ad2ea7a61e3c25cfda9a088"
 [[package]]
 name = "rustyline"
 version = "9.1.1"
-source = "git+https://github.com/rtfeldman/rustyline?tag=v9.1.1#7053ae0fe0ee710d38ed5845dd979113382994dc"
+source = "git+https://github.com/rtfeldman/rustyline?rev=e74333c#e74333c0d618896b88175bf06645108f996fe6d0"
 dependencies = [
  "bitflags",
  "cfg-if 1.0.0",
@@ -3848,7 +3850,7 @@ dependencies = [
 [[package]]
 name = "rustyline-derive"
 version = "0.6.0"
-source = "git+https://github.com/rtfeldman/rustyline?tag=v9.1.1#7053ae0fe0ee710d38ed5845dd979113382994dc"
+source = "git+https://github.com/rtfeldman/rustyline?rev=e74333c#e74333c0d618896b88175bf06645108f996fe6d0"
 dependencies = [
  "quote",
  "syn",
diff --git a/ast/Cargo.toml b/ast/Cargo.toml
index f0b82d7ca4..945f1f660e 100644
--- a/ast/Cargo.toml
+++ b/ast/Cargo.toml
@@ -21,10 +21,16 @@ roc_target = { path = "../compiler/roc_target" }
 roc_error_macros = { path = "../error_macros" }
 arrayvec = "0.7.2"
 bumpalo = { version = "3.8.0", features = ["collections"] }
-libc = "0.2.106"
 page_size = "0.4.2"
 snafu = { version = "0.6.10", features = ["backtraces"] }
 ven_graph = { path = "../vendor/pathfinding" }
+slab = "0.4.5"
 
 [dev-dependencies]
 indoc = "1.0.3"
+
+[target.'cfg(windows)'.dependencies]
+winapi = "0.3.9"
+
+[target.'cfg(unix)'.dependencies]
+libc = "0.2.106"
diff --git a/ast/src/mem_pool/pool.rs b/ast/src/mem_pool/pool.rs
index 6641627c76..ec55b04315 100644
--- a/ast/src/mem_pool/pool.rs
+++ b/ast/src/mem_pool/pool.rs
@@ -10,12 +10,10 @@
 ///
 /// Pages also use the node value 0 (all 0 bits) to mark nodes as unoccupied.
 /// This is important for performance.
-use libc::{MAP_ANONYMOUS, MAP_PRIVATE, PROT_READ, PROT_WRITE};
 use std::any::type_name;
 use std::ffi::c_void;
 use std::marker::PhantomData;
 use std::mem::{align_of, size_of, MaybeUninit};
-use std::ptr::null;
 
 pub const NODE_BYTES: usize = 32;
 
@@ -108,14 +106,30 @@ impl Pool {
             // addresses from the OS which will be lazily translated into
             // physical memory one 4096-byte page at a time, once we actually
             // try to read or write in that page's address range.
-            libc::mmap(
-                null::<c_void>() as *mut c_void,
-                bytes_to_mmap,
-                PROT_READ | PROT_WRITE,
-                MAP_PRIVATE | MAP_ANONYMOUS,
-                0,
-                0,
-            )
+            #[cfg(unix)]{
+                use libc::{MAP_ANONYMOUS, MAP_PRIVATE, PROT_READ, PROT_WRITE};
+
+                libc::mmap(
+                    std::ptr::null_mut(),
+                    bytes_to_mmap,
+                    PROT_READ | PROT_WRITE,
+                    MAP_PRIVATE | MAP_ANONYMOUS,
+                    0,
+                    0,
+                )
+            }
+            #[cfg(windows)]{
+                use winapi::um::memoryapi::{VirtualAlloc};
+                use winapi::um::winnt::{MEM_COMMIT, MEM_RESERVE};
+                use winapi::um::winnt::{PAGE_READWRITE};
+
+                VirtualAlloc(
+                    std::ptr::null_mut(),
+                    bytes_to_mmap,
+                    MEM_COMMIT | MEM_RESERVE,
+                    PAGE_READWRITE,
+                )
+            }
         } as *mut [MaybeUninit<u8>; NODE_BYTES];
 
         // This is our actual capacity, in nodes.
@@ -230,10 +244,22 @@ impl<T> std::ops::IndexMut<NodeId<T>> for Pool {
 impl Drop for Pool {
     fn drop(&mut self) {
         unsafe {
-            libc::munmap(
-                self.nodes as *mut c_void,
-                NODE_BYTES * self.capacity as usize,
-            );
+            #[cfg(unix)]{
+                libc::munmap(
+                    self.nodes as *mut c_void,
+                    NODE_BYTES * self.capacity as usize,
+                );
+            }
+            #[cfg(windows)]{
+                use winapi::um::memoryapi::{VirtualFree};
+                use winapi::um::winnt::{MEM_RELEASE};
+
+                VirtualFree(
+                    self.nodes as *mut c_void,
+                    NODE_BYTES * self.capacity as usize,
+                    MEM_RELEASE
+                );
+            }
         }
     }
 }
diff --git a/compiler/builtins/build.rs b/compiler/builtins/build.rs
index b117f888f7..90ee7c8d96 100644
--- a/compiler/builtins/build.rs
+++ b/compiler/builtins/build.rs
@@ -50,12 +50,17 @@ fn main() {
     );
 
     // OBJECT FILES
+    #[cfg(windows)]
+    const BUILTINS_HOST_FILE: &str = "builtins-host.obj";
+
+    #[cfg(not(windows))]
+    const BUILTINS_HOST_FILE: &str = "builtins-host.o";
 
     generate_object_file(
         &bitcode_path,
         "BUILTINS_HOST_O",
         "object",
-        "builtins-host.o",
+        BUILTINS_HOST_FILE,
     );
 
     generate_object_file(
diff --git a/linker/Cargo.toml b/linker/Cargo.toml
index 39cfdcdd37..697771fafa 100644
--- a/linker/Cargo.toml
+++ b/linker/Cargo.toml
@@ -24,7 +24,7 @@ roc_collections = { path = "../compiler/collections" }
 bumpalo = { version = "3.8.0", features = ["collections"] }
 clap = { version = "= 3.0.0-beta.5", default-features = false, features = ["std", "color", "suggestions"] }
 iced-x86 = { version = "1.15.0", default-features = false, features = ["std", "decoder", "op_code_info", "instr_info"] }
-memmap2 = "0.5.0"
+memmap2 = "0.5.3"
 object = { version = "0.26.2", features = ["read", "write"] }
 serde = { version = "1.0.130", features = ["derive"] }
 bincode = "1.3.3"
diff --git a/linker/src/lib.rs b/linker/src/lib.rs
index b9d6ee8519..e7abf8fe35 100644
--- a/linker/src/lib.rs
+++ b/linker/src/lib.rs
@@ -20,7 +20,6 @@ use std::io;
 use std::io::{BufReader, BufWriter};
 use std::mem;
 use std::os::raw::c_char;
-use std::os::unix::fs::PermissionsExt;
 use std::path::Path;
 use std::process::Command;
 use std::time::{Duration, SystemTime};
@@ -1627,9 +1626,14 @@ fn surgery_impl(
     let flushing_data_duration = flushing_data_start.elapsed().unwrap();
 
     // Make sure the final executable has permision to execute.
-    let mut perms = fs::metadata(out_filename)?.permissions();
-    perms.set_mode(perms.mode() | 0o111);
-    fs::set_permissions(out_filename, perms)?;
+    // TODO windows alternative?
+    #[cfg(target_family = "unix")]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let mut perms = fs::metadata(out_filename)?.permissions();
+        perms.set_mode(perms.mode() | 0o111);
+        fs::set_permissions(out_filename, perms)?;
+    }
 
     let total_duration = total_start.elapsed().unwrap();
 
diff --git a/repl_cli/Cargo.toml b/repl_cli/Cargo.toml
index 240d7113ba..dd5c3ee3c6 100644
--- a/repl_cli/Cargo.toml
+++ b/repl_cli/Cargo.toml
@@ -10,8 +10,8 @@ bumpalo = {version = "3.8.0", features = ["collections"]}
 const_format = "0.2.22"
 inkwell = {path = "../vendor/inkwell"}
 libloading = {version = "0.7.1"}
-rustyline = {git = "https://github.com/rtfeldman/rustyline", tag = "v9.1.1"}
-rustyline-derive = {git = "https://github.com/rtfeldman/rustyline", tag = "v9.1.1"}
+rustyline = {git = "https://github.com/rtfeldman/rustyline", rev = "e74333c"}
+rustyline-derive = {git = "https://github.com/rtfeldman/rustyline", rev = "e74333c"}
 target-lexicon = "0.12.2"
 
 roc_build = {path = "../compiler/build"}