diff --git a/src/evalbuffer.c b/src/evalbuffer.c
index bb6ff63..3fb037c 100644
--- a/src/evalbuffer.c
+++ b/src/evalbuffer.c
@@ -277,8 +277,12 @@
     void
 f_append(typval_T *argvars, typval_T *rettv)
 {
-    linenr_T	lnum = tv_get_lnum(&argvars[0]);
+    linenr_T	lnum;
 
+    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
+	return;
+
+    lnum = tv_get_lnum(&argvars[0]);
     set_buffer_lines(curbuf, lnum, TRUE, &argvars[1], rettv);
 }
 
@@ -291,6 +295,12 @@
     linenr_T	lnum;
     buf_T	*buf;
 
+    if (in_vim9script()
+	    && (check_for_buffer_arg(argvars, 0) == FAIL
+		|| check_for_lnum_arg(argvars, 1) == FAIL
+		|| check_for_string_or_number_or_list_arg(argvars, 2) == FAIL))
+	return;
+
     buf = tv_get_buf(&argvars[0], FALSE);
     if (buf == NULL)
 	rettv->vval.v_number = 1; // FAIL
@@ -307,8 +317,12 @@
     void
 f_bufadd(typval_T *argvars, typval_T *rettv)
 {
-    char_u *name = tv_get_string(&argvars[0]);
+    char_u *name;
 
+    if (in_vim9script() && check_for_string_arg(argvars, 0) == FAIL)
+	return;
+
+    name = tv_get_string(&argvars[0]);
     rettv->vval.v_number = buflist_add(*name == NUL ? NULL : name, 0);
 }
 
@@ -318,6 +332,9 @@
     void
 f_bufexists(typval_T *argvars, typval_T *rettv)
 {
+    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
+	return;
+
     rettv->vval.v_number = (find_buffer(&argvars[0]) != NULL);
 }
 
@@ -329,6 +346,9 @@
 {
     buf_T	*buf;
 
+    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
+	return;
+
     buf = find_buffer(&argvars[0]);
     rettv->vval.v_number = (buf != NULL && buf->b_p_bl);
 }
@@ -339,8 +359,12 @@
     void
 f_bufload(typval_T *argvars, typval_T *rettv UNUSED)
 {
-    buf_T	*buf = get_buf_arg(&argvars[0]);
+    buf_T	*buf;
 
+    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
+	return;
+
+    buf = get_buf_arg(&argvars[0]);
     if (buf != NULL)
 	buffer_ensure_loaded(buf);
 }
@@ -353,6 +377,9 @@
 {
     buf_T	*buf;
 
+    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
+	return;
+
     buf = find_buffer(&argvars[0]);
     rettv->vval.v_number = (buf != NULL && buf->b_ml.ml_mfp != NULL);
 }
@@ -366,6 +393,9 @@
     buf_T	*buf;
     typval_T	*tv = &argvars[0];
 
+    if (in_vim9script() && check_for_opt_buffer_arg(argvars, 0) == FAIL)
+	return;
+
     if (tv->v_type == VAR_UNKNOWN)
 	buf = curbuf;
     else
@@ -421,6 +451,9 @@
     int		winnr = 0;
     buf_T	*buf;
 
+    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
+	return;
+
     buf = tv_get_buf_from_arg(&argvars[0]);
     FOR_ALL_WINDOWS(wp)
     {
@@ -636,8 +669,7 @@
 	return;
 
     if (in_vim9script()
-	    && argvars[0].v_type != VAR_UNKNOWN
-	    && check_for_buffer_or_dict_arg(argvars, 0) == FAIL)
+	    && check_for_opt_buffer_or_dict_arg(argvars, 0) == FAIL)
 	return;
 
     // List of all the buffers or selected buffers
@@ -808,6 +840,12 @@
     linenr_T	lnum;
     buf_T	*buf;
 
+    if (in_vim9script()
+	    && (check_for_buffer_arg(argvars, 0) == FAIL
+		|| check_for_lnum_arg(argvars, 1) == FAIL
+		|| check_for_string_or_number_or_list_arg(argvars, 2) == FAIL))
+	return;
+
     buf = tv_get_buf(&argvars[0], FALSE);
     if (buf == NULL)
 	rettv->vval.v_number = 1; // FAIL
@@ -824,8 +862,12 @@
     void
 f_setline(typval_T *argvars, typval_T *rettv)
 {
-    linenr_T	lnum = tv_get_lnum(&argvars[0]);
+    linenr_T	lnum;
 
+    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
+	return;
+
+    lnum = tv_get_lnum(&argvars[0]);
     set_buffer_lines(curbuf, lnum, FALSE, &argvars[1], rettv);
 }
 #endif  // FEAT_EVAL