diff --git a/src/opts.rs b/src/opts.rs
index c709fd0c22..88f4eb74b7 100644
--- a/src/opts.rs
+++ b/src/opts.rs
@@ -233,6 +233,111 @@ where
     Ok(())
 }
 
+/// Get the maximum mmap window size
+///
+/// # Safety
+/// This function is reading a C global without synchronization, so it is not
+/// thread safe, and should only be called before any thread is spawned.
+pub unsafe fn get_mwindow_size() -> Result<libc::size_t, Error> {
+    crate::init();
+
+    let mut size = 0;
+
+    try_call!(raw::git_libgit2_opts(
+        raw::GIT_OPT_GET_MWINDOW_SIZE as libc::c_int,
+        &mut size
+    ));
+
+    Ok(size)
+}
+
+/// Set the maximum mmap window size
+///
+/// # Safety
+/// This function is modifying a C global without synchronization, so it is not
+/// thread safe, and should only be called before any thread is spawned.
+pub unsafe fn set_mwindow_size(size: libc::size_t) -> Result<(), Error> {
+    crate::init();
+
+    try_call!(raw::git_libgit2_opts(
+        raw::GIT_OPT_SET_MWINDOW_SIZE as libc::c_int,
+        size
+    ));
+
+    Ok(())
+}
+
+/// Get the maximum memory that will be mapped in total by the library
+///
+/// # Safety
+/// This function is reading a C global without synchronization, so it is not
+/// thread safe, and should only be called before any thread is spawned.
+pub unsafe fn get_mwindow_mapped_limit() -> Result<libc::size_t, Error> {
+    crate::init();
+
+    let mut limit = 0;
+
+    try_call!(raw::git_libgit2_opts(
+        raw::GIT_OPT_GET_MWINDOW_MAPPED_LIMIT as libc::c_int,
+        &mut limit
+    ));
+
+    Ok(limit)
+}
+
+/// Set the maximum amount of memory that can be mapped at any time
+/// by the library.
+///
+/// # Safety
+/// This function is modifying a C global without synchronization, so it is not
+/// thread safe, and should only be called before any thread is spawned.
+pub unsafe fn set_mwindow_mapped_limit(limit: libc::size_t) -> Result<(), Error> {
+    crate::init();
+
+    try_call!(raw::git_libgit2_opts(
+        raw::GIT_OPT_SET_MWINDOW_MAPPED_LIMIT as libc::c_int,
+        limit
+    ));
+
+    Ok(())
+}
+
+/// Get the maximum number of files that will be mapped at any time by the
+/// library.
+///
+/// # Safety
+/// This function is reading a C global without synchronization, so it is not
+/// thread safe, and should only be called before any thread is spawned.
+pub unsafe fn get_mwindow_file_limit() -> Result<libc::size_t, Error> {
+    crate::init();
+
+    let mut limit = 0;
+
+    try_call!(raw::git_libgit2_opts(
+        raw::GIT_OPT_GET_MWINDOW_FILE_LIMIT as libc::c_int,
+        &mut limit
+    ));
+
+    Ok(limit)
+}
+
+/// Set the maximum number of files that can be mapped at any time
+/// by the library. The default (0) is unlimited.
+///
+/// # Safety
+/// This function is modifying a C global without synchronization, so it is not
+/// thread safe, and should only be called before any thread is spawned.
+pub unsafe fn set_mwindow_file_limit(limit: libc::size_t) -> Result<(), Error> {
+    crate::init();
+
+    try_call!(raw::git_libgit2_opts(
+        raw::GIT_OPT_SET_MWINDOW_FILE_LIMIT as libc::c_int,
+        limit
+    ));
+
+    Ok(())
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
@@ -241,4 +346,28 @@ mod test {
     fn smoke() {
         strict_hash_verification(false);
     }
+
+    #[test]
+    fn mwindow_size() {
+        unsafe {
+            assert!(set_mwindow_size(1024).is_ok());
+            assert!(get_mwindow_size().unwrap() == 1024);
+        }
+    }
+
+    #[test]
+    fn mwindow_mapped_limit() {
+        unsafe {
+            assert!(set_mwindow_mapped_limit(1024).is_ok());
+            assert!(get_mwindow_mapped_limit().unwrap() == 1024);
+        }
+    }
+
+    #[test]
+    fn mwindow_file_limit() {
+        unsafe {
+            assert!(set_mwindow_file_limit(1024).is_ok());
+            assert!(get_mwindow_file_limit().unwrap() == 1024);
+        }
+    }
 }