diff --git a/src/sys/mman.rs b/src/sys/mman.rs
index 33ac21de07..0d9e9d3979 100644
--- a/src/sys/mman.rs
+++ b/src/sys/mman.rs
@@ -139,14 +139,22 @@ libc_bitflags!{
     }
 }
 
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "netbsd"))]
 libc_bitflags!{
     /// Options for `mremap()`.
     pub struct MRemapFlags: c_int {
         /// Permit the kernel to relocate the mapping to a new virtual address, if necessary.
+        #[cfg(target_os = "linux")]
         MREMAP_MAYMOVE;
         /// Place the mapping at exactly the address specified in `new_address`.
+        #[cfg(target_os = "linux")]
         MREMAP_FIXED;
+        /// Permits to use the old and new address as hints to relocate the mapping.
+        #[cfg(target_os = "netbsd")]
+        MAP_FIXED;
+        /// Allows to duplicate the mapping to be able to apply different flags on the copy.
+        #[cfg(target_os = "netbsd")]
+        MAP_REMAPDUP;
     }
 }
 
@@ -334,7 +342,7 @@ pub unsafe fn mmap(addr: *mut c_void, length: size_t, prot: ProtFlags, flags: Ma
 ///
 /// See the `mremap(2)` [man page](https://man7.org/linux/man-pages/man2/mremap.2.html) for
 /// detailed requirements.
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "netbsd"))]
 pub unsafe fn mremap(
     addr: *mut c_void,
     old_size: size_t,
@@ -342,7 +350,16 @@ pub unsafe fn mremap(
     flags: MRemapFlags,
     new_address: Option<* mut c_void>,
 ) -> Result<*mut c_void> {
+    #[cfg(target_os = "linux")]
     let ret = libc::mremap(addr, old_size, new_size, flags.bits(), new_address.unwrap_or(std::ptr::null_mut()));
+    #[cfg(target_os = "netbsd")]
+    let ret = libc::mremap(
+        addr,
+        old_size,
+        new_address.unwrap_or(std::ptr::null_mut()),
+        new_size,
+        flags.bits(),
+        );
 
     if ret == libc::MAP_FAILED {
         Err(Error::from(Errno::last()))
diff --git a/test/sys/test_mman.rs b/test/sys/test_mman.rs
index 152fff69c2..4d1409487e 100644
--- a/test/sys/test_mman.rs
+++ b/test/sys/test_mman.rs
@@ -20,7 +20,7 @@ fn test_mmap_anonymous() {
 }
 
 #[test]
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "netbsd"))]
 fn test_mremap_grow() {
     const ONE_K : size_t = 1024;
     let slice : &mut[u8] = unsafe {
@@ -35,9 +35,14 @@ fn test_mremap_grow() {
     assert_eq !(slice[ONE_K - 1], 0xFF);
 
     let slice : &mut[u8] = unsafe {
+        #[cfg(target_os = "linux")]
         let mem = mremap(slice.as_mut_ptr() as * mut c_void, ONE_K, 10 * ONE_K,
                          MRemapFlags::MREMAP_MAYMOVE, None)
                       .unwrap();
+        #[cfg(target_os = "netbsd")]
+        let mem = mremap(slice.as_mut_ptr() as * mut c_void, ONE_K, 10 * ONE_K,
+                         MRemapFlags::MAP_REMAPDUP, None)
+                      .unwrap();
         std::slice::from_raw_parts_mut(mem as * mut u8, 10 * ONE_K)
     };
 
@@ -51,7 +56,7 @@ fn test_mremap_grow() {
 }
 
 #[test]
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "netbsd"))]
 fn test_mremap_shrink() {
     const ONE_K : size_t = 1024;
     let slice : &mut[u8] = unsafe {
@@ -66,11 +71,16 @@ fn test_mremap_shrink() {
     assert_eq !(slice[ONE_K - 1], 0xFF);
 
     let slice : &mut[u8] = unsafe {
+        #[cfg(target_os = "linux")]
         let mem = mremap(slice.as_mut_ptr() as * mut c_void, 10 * ONE_K, ONE_K,
                          MRemapFlags::empty(), None)
                       .unwrap();
         // Since we didn't supply MREMAP_MAYMOVE, the address should be the
         // same.
+        #[cfg(target_os = "linux")]
+        let mem = mremap(slice.as_mut_ptr() as * mut c_void, 10 * ONE_K, ONE_K,
+                         MRemapFlags::MAP_FIXED), None)
+                      .unwrap();
         assert_eq !(mem, slice.as_mut_ptr() as * mut c_void);
         std::slice::from_raw_parts_mut(mem as * mut u8, ONE_K)
     };