diff --git a/src/errors.h b/src/errors.h
index e09ef53..1d6a3a3 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -689,3 +689,5 @@
 	INIT(= N_("E1246: Cannot find variable to (un)lock: %s"));
 EXTERN char e_line_number_out_of_range[]
 	INIT(= N_("E1247: Line number out of range"));
+EXTERN char e_closure_called_from_invalid_context[]
+	INIT(= N_("E1248: Closure called from invalid context"));
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 51b95ab..651da05 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -2384,6 +2384,21 @@
   delfunc g:Inner
 enddef
 
+def Test_closure_called_from_legacy()
+  var lines =<< trim END
+      vim9script
+      def Func()
+        var outer = 'foo'
+        var F = () => {
+              outer = 'bar'
+            }
+        execute printf('call %s()', string(F))
+      enddef
+      Func()
+  END
+  CheckScriptFailure(lines, 'E1248')
+enddef
+
 def Test_failure_in_called_function()
   # this was using the frame index as the return value
   var lines =<< trim END
diff --git a/src/version.c b/src/version.c
index d977c65..810567f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3720,
+/**/
     3719,
 /**/
     3718,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 4b2763b..bd7f71e 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -2733,7 +2733,13 @@
 		    if (outer == NULL)
 		    {
 			SOURCING_LNUM = iptr->isn_lnum;
-			iemsg("LOADOUTER depth more than scope levels");
+			if (ectx->ec_frame_idx == ectx->ec_initial_frame_idx
+						 || ectx->ec_outer_ref == NULL)
+			    // Possibly :def function called from legacy
+			    // context.
+			    emsg(_(e_closure_called_from_invalid_context));
+			else
+			    iemsg("LOADOUTER depth more than scope levels");
 			goto theend;
 		    }
 		    tv = ((typval_T *)outer->out_stack->ga_data)