diff --git a/regress/usr.sbin/btrace/Makefile b/regress/usr.sbin/btrace/Makefile
index 29f90cef4..e1d399910 100644
--- a/regress/usr.sbin/btrace/Makefile
+++ b/regress/usr.sbin/btrace/Makefile
@@ -1,11 +1,11 @@
-# $OpenBSD: Makefile,v 1.27 2023/08/13 09:49:47 mpi Exp $
+# $OpenBSD: Makefile,v 1.28 2023/08/28 21:23:46 dv Exp $
 
 BTRACE?=		 /usr/sbin/btrace
 ALLOWDT!=		sysctl -n kern.allowdt 2>/dev/null
 
 # scripts that don't need /dev/dt
-BT_LANG_SCRIPTS=	arithm beginend boolean comments delete exit \
-			histempty if \
+BT_LANG_SCRIPTS=	arithm beginend beginend-argn boolean comments delete \
+			exit histempty if \
 			map mapclear mapempty mapsyntax mapzero map-unnamed \
 			maxoperand min+max+sum multismts nsecs+var \
 			precedence print read-map-after-clear staticv-empty \
diff --git a/regress/usr.sbin/btrace/beginend-argn.bt b/regress/usr.sbin/btrace/beginend-argn.bt
new file mode 100644
index 000000000..7260ad401
--- /dev/null
+++ b/regress/usr.sbin/btrace/beginend-argn.bt
@@ -0,0 +1,8 @@
+// Test catching invalid use of argN in BEGIN and END contexts.
+BEGIN {
+	print(arg0);
+}
+
+END {
+	print(arg0);
+}
diff --git a/regress/usr.sbin/btrace/beginend-argn.ok b/regress/usr.sbin/btrace/beginend-argn.ok
new file mode 100644
index 000000000..3c0fb6780
--- /dev/null
+++ b/regress/usr.sbin/btrace/beginend-argn.ok
@@ -0,0 +1,6 @@
+beginend-argn.bt:3:11: the arg0 builtin cannot be used with BEGIN or END probes:
+	print(arg0);
+                 ^
+beginend-argn.bt:7:11: the arg0 builtin cannot be used with BEGIN or END probes:
+	print(arg0);
+                 ^
diff --git a/usr.sbin/btrace/bt_parse.y b/usr.sbin/btrace/bt_parse.y
index 959f6e4a4..b2c3bef3b 100644
--- a/usr.sbin/btrace/bt_parse.y
+++ b/usr.sbin/btrace/bt_parse.y
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bt_parse.y,v 1.50 2023/08/13 13:19:23 dv Exp $	*/
+/*	$OpenBSD: bt_parse.y,v 1.51 2023/08/28 21:23:46 dv Exp $	*/
 
 /*
  * Copyright (c) 2019-2021 Martin Pieuchot <mpi@openbsd.org>
@@ -109,7 +109,8 @@ typedef struct {
 static void	 yyerror(const char *, ...);
 static int	 yylex(void);
 
-static int pflag;
+static int 	 pflag = 0;		/* probe parsing context flag */
+static int 	 beflag = 0;		/* BEGIN/END parsing context flag */
 %}
 
 %token	<v.i>		ERROR ENDFILT
@@ -137,7 +138,7 @@ grammar	: /* empty */
 	| grammar error
 	;
 
-rule	: plist filter action		{ br_new($1, $2, $3); }
+rule	: plist filter action		{ br_new($1, $2, $3); beflag = 0; }
 	;
 
 beginend: BEGIN	| END ;
@@ -147,7 +148,7 @@ plist	: plist ',' probe		{ $$ = bp_append($1, $3); }
 	;
 
 probe	: { pflag = 1; } pname		{ $$ = $2; pflag = 0; }
-	| beginend			{ $$ = bp_new(NULL, NULL, NULL, $1); }
+	| { beflag = 1; } beginend	{ $$ = bp_new(NULL, NULL, NULL, $2); }
 	;
 
 pname	: STRING ':' STRING ':' STRING	{ $$ = bp_new($1, $3, $5, 0); }
@@ -962,6 +963,12 @@ again:
 				yylval.v.string = kwp->word;
 				return STRING;
 			}
+		} else if (beflag) {
+			/* Interpret tokens in a BEGIN/END context. */
+			if (kwp->type >= B_AT_BI_ARG0 &&
+			    kwp->type <= B_AT_BI_ARG9)
+				yyerror("the %s builtin cannot be used with "
+				    "BEGIN or END probes", kwp->word);
 		}
 		yylval.v.i = kwp->type;
 		return kwp->token;