diff --git a/libc/bionic/grp_pwd.cpp b/libc/bionic/grp_pwd.cpp
index 600693c..82ee7ba 100644
--- a/libc/bionic/grp_pwd.cpp
+++ b/libc/bionic/grp_pwd.cpp
@@ -609,6 +609,8 @@
 }
 
 // All users are in just one group, the one passed in.
+// In practice, id(1) will show you in a lot more groups, because adbd
+// adds you to a lot of supplementary groups when dropping privileges.
 int getgrouplist(const char* /*user*/, gid_t group, gid_t* groups, int* ngroups) {
   if (*ngroups < 1) {
     *ngroups = 1;
@@ -618,6 +620,12 @@
   return (*ngroups = 1);
 }
 
+// See getgrouplist() to understand why we don't call it.
+int initgroups(const char* /*user*/, gid_t group) {
+  gid_t groups[] = {group};
+  return setgroups(1, groups);
+}
+
 char* getlogin() { // NOLINT: implementing bad function.
   passwd *pw = getpwuid(getuid()); // NOLINT: implementing bad function in terms of bad function.
   return pw ? pw->pw_name : nullptr;