diff --git a/Makefile b/Makefile
index 98278d6d5..66cd57ac0 100644
--- a/Makefile
+++ b/Makefile
@@ -97,9 +97,10 @@ command     = sh -c '$(1)'
 
 # Main exe build rule
 define EXE_BUILD
+-include build/$(1).d
 ifeq ($(wildcard $(1)/Makefile),)
 build/$(1): $(1)/$(1).rs | build
-	$(call command,$(RUSTC) $(RUSTCFLAGS) -o build/$(1) $(1)/$(1).rs)
+	$(call command,$(RUSTC) $(RUSTCFLAGS) --dep-info build/$(1).d -o build/$(1) $(1)/$(1).rs)
 clean_$(1):
 else
 build/$(1): $(1)/$(1).rs | build
@@ -110,8 +111,9 @@ endif
 endef
 
 define CRATE_BUILD
+-include build/$(1).d
 build/$(2): $(1)/$(1).rs | build
-	$(call command,$(RUSTC) $(RUSTCFLAGS) --crate-type rlib $(1)/$(1).rs --out-dir build)
+	$(call command,$(RUSTC) $(RUSTCFLAGS) --crate-type rlib --dep-info build/$(1).d $(1)/$(1).rs --out-dir build)
 endef
 
 # Test exe built rules
@@ -129,8 +131,10 @@ all: $(EXES_PATHS)
 else
 all: build/uutils
 
+-include build/uutils.d
+
 build/uutils: uutils/uutils.rs $(addprefix build/, $(foreach crate,$(CRATES),$(shell $(RUSTC) --crate-type rlib --crate-file-name $(crate)/$(crate).rs)))
-	$(RUSTC) $(RUSTCFLAGS) -L build/ uutils/uutils.rs -o $@
+	$(RUSTC) $(RUSTCFLAGS) -L build/ --dep-info $@.d uutils/uutils.rs -o $@
 endif
 
 test: tmp $(addprefix test_,$(TESTS))
diff --git a/common/c_types.rs b/common/c_types.rs
index 5a9e4bb37..bf91354b9 100644
--- a/common/c_types.rs
+++ b/common/c_types.rs
@@ -5,6 +5,7 @@ extern crate libc;
 use self::libc::{
     c_char,
     c_int,
+    int32_t,
     uid_t,
     gid_t,
 };
@@ -83,12 +84,17 @@ pub struct c_tm {
 extern {
     pub fn getpwuid(uid: uid_t) -> *c_passwd;
     pub fn getpwnam(login: *c_char) -> *c_passwd;
-    pub fn getgrouplist(name:   *c_char,
-                        basegid: gid_t,
-                        groups: *mut gid_t,
-                        ngroups: *mut c_int) -> c_int;
     pub fn getgrgid(gid: gid_t) -> *c_group;
     pub fn getgrnam(name: *c_char) -> *c_group;
+    pub fn getgrouplist(name: *c_char,
+                        gid: gid_t,
+                        groups: *mut gid_t,
+                        ngroups: *mut c_int) -> c_int;
+}
+
+#[cfg(target_os = "macos")]
+extern {
+    pub fn getgroupcount(name: *c_char, gid: gid_t) -> int32_t;
 }
 
 pub fn get_pw_from_args(free: &Vec<String>) -> Option<c_passwd> {
@@ -137,17 +143,37 @@ pub fn get_group(groupname: &str) -> Option<c_group> {
     }
 }
 
-pub fn get_group_list(name: *c_char, gid: gid_t) -> Result<Vec<gid_t>, int> {
-    let mut ngroups = 0 as c_int;
+pub fn get_group_list(name: *c_char, gid: gid_t) -> Vec<gid_t> {
+    let mut ngroups: c_int = 32;
+    let mut groups: Vec<gid_t> = Vec::with_capacity(ngroups as uint);
 
-    unsafe { getgrouplist(name, gid, 0 as *mut gid_t, &mut ngroups) };
-    let mut groups = Vec::from_elem(ngroups as uint, 0 as gid_t);
-    let err = unsafe { getgrouplist(name, gid, groups.as_mut_ptr(), &mut ngroups) };
-    if err == -1 {
-        Err(os::errno())
+    if unsafe { get_group_list_internal(name, gid, groups.as_mut_ptr(), &mut ngroups) } == -1 {
+        groups.reserve(ngroups as uint);
+        unsafe { get_group_list_internal(name, gid, groups.as_mut_ptr(), &mut ngroups); }
     } else {
         groups.truncate(ngroups as uint);
-        Ok(groups)
+    }
+    unsafe { groups.set_len(ngroups as uint); }
+
+    groups
+}
+
+#[cfg(target_os = "linux")]
+#[inline(always)]
+unsafe fn get_group_list_internal(name: *c_char, gid: gid_t, groups: *mut gid_t, grcnt: *mut c_int) -> c_int {
+    getgrouplist(name, gid, groups, grcnt)
+}
+
+#[cfg(target_os = "macos")]
+unsafe fn get_group_list_internal(name: *c_char, gid: gid_t, groups: *mut gid_t, grcnt: *mut c_int) -> c_int {
+    let ngroups = getgroupcount(name, gid);
+    let oldsize = *grcnt;
+    *grcnt = ngroups;
+    if oldsize >= ngroups {
+        getgrouplist(name, gid, groups, grcnt);
+        0
+    } else {
+        -1
     }
 }
 
@@ -170,7 +196,7 @@ pub fn get_groups() -> Result<Vec<gid_t>, int> {
 pub fn group(possible_pw: Option<c_passwd>, nflag: bool) {
 
     let groups = match possible_pw {
-        Some(pw) => get_group_list(pw.pw_name, pw.pw_gid),
+        Some(pw) => Ok(get_group_list(pw.pw_name, pw.pw_gid)),
         None => get_groups(),
     };
 
diff --git a/id/id.rs b/id/id.rs
index c1610c15f..e75ba70a2 100644
--- a/id/id.rs
+++ b/id/id.rs
@@ -21,7 +21,6 @@ extern crate libc;
 use std::os;
 use std::ptr::read;
 use libc::{
-    c_int,
     uid_t,
     getgid,
     getuid
@@ -342,7 +341,7 @@ fn id_print(possible_pw: Option<c_passwd>,
     }
 
     let groups = match possible_pw {
-        Some(pw) => get_group_list(pw.pw_name, pw.pw_gid),
+        Some(pw) => Ok(get_group_list(pw.pw_name, pw.pw_gid)),
         None => get_groups(),
     };