diff --git a/src/unix/bsd/apple/mod.rs b/src/unix/bsd/apple/mod.rs
index 9b36e78133d11547abfccd74b3b5de2472e427f2..918f05e7a3f7b5a8ba5f7a9964ab89589d46bcb5 100644
--- a/src/unix/bsd/apple/mod.rs
+++ b/src/unix/bsd/apple/mod.rs
@@ -1798,6 +1798,10 @@ extern {
     pub fn fremovexattr(filedes: ::c_int, name: *const ::c_char,
                         flags: ::c_int) -> ::c_int;
 
+    pub fn getgrouplist(name: *const ::c_char,
+                        basegid: ::c_int,
+                        groups: *mut ::c_int,
+                        ngroups: *mut ::c_int) -> ::c_int;
     pub fn initgroups(user: *const ::c_char, basegroup: ::c_int) -> ::c_int;
 
     #[cfg_attr(all(target_os = "macos", target_arch = "x86"),
diff --git a/src/unix/bsd/freebsdlike/mod.rs b/src/unix/bsd/freebsdlike/mod.rs
index 9f3891546a335da530da510dc63f0a957885cfd9..2876a62d910e86039469b16a0ad081b118d7f823 100644
--- a/src/unix/bsd/freebsdlike/mod.rs
+++ b/src/unix/bsd/freebsdlike/mod.rs
@@ -964,6 +964,10 @@ extern {
     pub fn setutxent();
     pub fn setresgid(rgid: ::gid_t, egid: ::gid_t, sgid: ::gid_t) -> ::c_int;
     pub fn setresuid(ruid: ::uid_t, euid: ::uid_t, suid: ::uid_t) -> ::c_int;
+    pub fn getgrouplist(name: *const ::c_char,
+                        basegid: ::gid_t,
+                        groups: *mut ::gid_t,
+                        ngroups: *mut ::c_int) -> ::c_int;
     pub fn initgroups(name: *const ::c_char, basegid: ::gid_t) -> ::c_int;
 }
 
diff --git a/src/unix/bsd/netbsdlike/mod.rs b/src/unix/bsd/netbsdlike/mod.rs
index b60354b3a70982797408b3de1bd973d3079f3c6b..35116239cfa2e12cf5a38a097c41146e0774716d 100644
--- a/src/unix/bsd/netbsdlike/mod.rs
+++ b/src/unix/bsd/netbsdlike/mod.rs
@@ -617,6 +617,10 @@ extern {
                                    abstime: *const ::timespec) -> ::c_int;
     pub fn pipe2(fds: *mut ::c_int, flags: ::c_int) -> ::c_int;
 
+    pub fn getgrouplist(name: *const ::c_char,
+                        basegid: ::gid_t,
+                        groups: *mut ::gid_t,
+                        ngroups: *mut ::c_int) -> ::c_int;
     pub fn initgroups(name: *const ::c_char, basegid: ::gid_t) -> ::c_int;
 }
 
diff --git a/src/unix/notbsd/mod.rs b/src/unix/notbsd/mod.rs
index 839bafadf79caf8d55bf41816ff115ef574eb822..bbfc4f1873d00b4bd402ed8f289017393c1997d1 100644
--- a/src/unix/notbsd/mod.rs
+++ b/src/unix/notbsd/mod.rs
@@ -880,6 +880,10 @@ extern {
     pub fn memalign(align: ::size_t, size: ::size_t) -> *mut ::c_void;
     pub fn setgroups(ngroups: ::size_t,
                      ptr: *const ::gid_t) -> ::c_int;
+    pub fn getgrouplist(user: *const ::c_char,
+                        group: ::gid_t,
+                        groups: *mut ::gid_t,
+                        ngroups: *mut ::c_int) -> ::c_int;
     pub fn initgroups(user: *const ::c_char, group: ::gid_t) -> ::c_int;
     pub fn sched_setscheduler(pid: ::pid_t,
                               policy: ::c_int,