diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 3758697..9196184 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -222,6 +222,38 @@
 enddef
 
 
+def FuncWithForwardCall(): string
+  return DefinedLater("yes")
+enddef
+
+def DefinedLater(arg: string): string
+  return arg
+enddef
+
+def Test_disassemble_update_instr()
+  let res = execute('disass FuncWithForwardCall')
+  assert_match('FuncWithForwardCall.*'
+        \ .. 'return DefinedLater("yes").*'
+        \ .. '\d PUSHS "yes".*'
+        \ .. '\d UCALL DefinedLater(argc 1).*'
+        \ .. '\d CHECKTYPE string stack\[-1].*'
+        \ .. '\d RETURN.*'
+        \, res)
+
+  " Calling the function will change UCALL into the faster DCALL
+  assert_equal('yes', FuncWithForwardCall())
+
+  res = execute('disass FuncWithForwardCall')
+  assert_match('FuncWithForwardCall.*'
+        \ .. 'return DefinedLater("yes").*'
+        \ .. '\d PUSHS "yes".*'
+        \ .. '\d DCALL DefinedLater(argc 1).*'
+        \ .. '\d CHECKTYPE string stack\[-1].*'
+        \ .. '\d RETURN.*'
+        \, res)
+enddef
+
+
 def FuncWithDefault(arg: string = 'default'): string
   return arg
 enddef
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 53ee511..f1b21d4 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -212,6 +212,19 @@
   return a:arg
 endfunc
 
+def FuncWithForwardCall()
+  return DefinedEvenLater("yes")
+enddef
+
+def DefinedEvenLater(arg: string): string
+  return arg
+enddef
+
+def Test_error_in_nested_function()
+  " Error in called function requires unwinding the call stack.
+  assert_fails('call FuncWithForwardCall()', 'E1029')
+enddef
+
 def Test_return_type_wrong()
   CheckScriptFailure(['def Func(): number', 'return "a"', 'enddef'], 'expected number but got string')
   CheckScriptFailure(['def Func(): string', 'return 1', 'enddef'], 'expected string but got number')