diff --git a/UPDATING b/UPDATING
--- a/UPDATING
+++ b/UPDATING
@@ -27,6 +27,13 @@
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20250403:
+	ps(1)'s default list of processes now comes from matching its effective
+	user ID instead of its real user ID with the effective user ID of all
+	processes, in accordance with POSIX.  As ps(1) itself is not installed
+	setuid, this only affects processes having different real and effective
+	user IDs that launch ps(1) processes.
+
 20250314:
 	We now use LLVM's binary utilities (nm, objcopy, etc.) by default.
 	The WITHOUT_LLVM_BINUTILS src.conf(5) knob can be used to revert to
diff --git a/bin/ps/ps.c b/bin/ps/ps.c
--- a/bin/ps/ps.c
+++ b/bin/ps/ps.c
@@ -503,13 +503,14 @@
 		 */
 		nselectors = 0;
 	else if (nselectors == 0) {
-		/* Default is to request our processes only. */
-		uidlist.l.ptr = malloc(sizeof(uid_t));
-		if (uidlist.l.ptr == NULL)
-			xo_errx(1, "malloc failed");
+		/*
+		 * Default is to request our processes only.  As per POSIX, we
+		 * match processes by their effective user IDs and we use our
+		 * effective user ID as our own identity.
+		 */
+		expand_list(&uidlist);
+		*uidlist.l.uids = geteuid();
 		nselectors = 1;
-		uidlist.count = uidlist.maxcount = 1;
-		*uidlist.l.uids = getuid();
 	}
 
 	/*