diff --git a/libc/calls/getgroups.c b/libc/calls/getgroups.c
index 1e052bf7e..e69f5f642 100644
--- a/libc/calls/getgroups.c
+++ b/libc/calls/getgroups.c
@@ -25,7 +25,7 @@
 #include "libc/sysv/errfuns.h"
 
 /**
- * Get list of supplementary group IDs
+ * Gets list of supplementary group IDs
  *
  * @param size - maximum number of items that can be stored in list
  * @param list - buffer to store output gid_t
diff --git a/libc/calls/setgroups.c b/libc/calls/setgroups.c
index fb9b9cb69..ace1f08d1 100644
--- a/libc/calls/setgroups.c
+++ b/libc/calls/setgroups.c
@@ -25,10 +25,16 @@
 #include "libc/sysv/errfuns.h"
 
 /**
- * Set list of supplementary group IDs
+ * Sets list of supplementary group IDs.
  *
- * @param size - number of items in list
- * @param list - input set of gid_t to set
+ * On recent versions of Linux only, it's possible to say:
+ *
+ *     setgroups(0, NULL);
+ *
+ * Which will cause subsequent calls to `EPERM`.
+ *
+ * @param size number of items in list
+ * @param list input set of gid_t to set
  * @return -1 w/ EFAULT
  */
 int setgroups(size_t size, const uint32_t list[]) {
diff --git a/test/libc/calls/getgroups_test.c b/test/libc/calls/getgroups_test.c
index 8ad5dd08e..82c7d3a04 100644
--- a/test/libc/calls/getgroups_test.c
+++ b/test/libc/calls/getgroups_test.c
@@ -18,30 +18,14 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/dce.h"
-#include "libc/errno.h"
+#include "libc/macros.internal.h"
 #include "libc/testlib/testlib.h"
 
 TEST(getgroups, test) {
-  int rc;
-  uint32_t res[1000];
-  rc = getgroups(0, NULL);
-  if (IsLinux() || IsNetbsd() || IsOpenbsd() || IsFreebsd() || IsXnu()) {
-    EXPECT_NE(-1, rc);
-    EXPECT_NE(-1, getgroups(sizeof(res) / sizeof(res[0]), res));
-  } else {
-    EXPECT_EQ(-1, rc);
-    EXPECT_EQ(ENOSYS, errno);
-  }
-}
-
-TEST(setgroups, test) {
-  int rc;
-  uint32_t src[5];
-  EXPECT_EQ(-1, setgroups(0, NULL));
-  if (IsLinux() || IsNetbsd() || IsOpenbsd() || IsFreebsd() || IsXnu()) {
-    EXPECT_EQ(EPERM, errno);
-    EXPECT_EQ(-1, setgroups(sizeof(src) / sizeof(src[0]), src));
-  } else {
-    EXPECT_EQ(ENOSYS, errno);
-  }
+  int n;
+  if (IsWindows()) return;
+  uint32_t G[500];
+  EXPECT_GT((n = getgroups(ARRAYLEN(G), G)), 0);
+  if (getuid()) return;  // this needs root
+  EXPECT_SYS(0, 0, setgroups(n, G));
 }