diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 4a5546b..4d5ff14 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1492,6 +1492,29 @@
         'x = filter(["bbb"], (_, v) => v =~ x)'])
 enddef
 
+def Test_lambda_invalid_block()
+  var lines =<< trim END
+      timer_start(0, (_) => { # echo
+          echo 'yes'
+        })
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
+      timer_start(0, (_) => { " echo
+          echo 'yes'
+        })
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E488: Trailing characters: " echo')
+
+  lines =<< trim END
+      timer_start(0, (_) => { | echo
+          echo 'yes'
+        })
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E488: Trailing characters: | echo')
+enddef
+
 def Test_pass_legacy_lambda_to_def_func()
   var lines =<< trim END
       vim9script
diff --git a/src/userfunc.c b/src/userfunc.c
index 83221a8..cc90b95 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -1166,6 +1166,7 @@
 	garray_T    *default_args,
 	char_u	    *ret_type)
 {
+    char_u	*start = *arg;
     int		evaluate = (evalarg->eval_flags & EVAL_EVALUATE);
     garray_T	*gap = &evalarg->eval_ga;
     garray_T	*freegap = &evalarg->eval_freega;
@@ -1179,9 +1180,10 @@
     int		lnum_save = -1;
     linenr_T	sourcing_lnum_top = SOURCING_LNUM;
 
-    if (!ends_excmd2(*arg, skipwhite(*arg + 1)))
+    *arg = skipwhite(*arg + 1);
+    if (**arg == '|' || !ends_excmd2(start, *arg))
     {
-	semsg(_(e_trailing_characters_str), *arg + 1);
+	semsg(_(e_trailing_characters_str), *arg);
 	return FAIL;
     }
 
diff --git a/src/version.c b/src/version.c
index 505185d..57d8259 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    553,
+/**/
     552,
 /**/
     551,