diff --git a/src/terminal.c b/src/terminal.c
index f007bf2..bc57d64 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -3779,7 +3779,7 @@
     argvars[0].v_type = VAR_NUMBER;
     argvars[0].vval.v_number = term->tl_buffer->b_fnum;
     argvars[1] = item->li_next->li_tv;
-    if (call_func(func, (int)STRLEN(func), &rettv,
+    if (call_func(func, -1, &rettv,
 		2, argvars, /* argv_func */ NULL,
 		/* firstline */ 1, /* lastline */ 1,
 		&doesrange, /* evaluate */ TRUE,