7 files changed, 15 insertions, 11 deletions
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index cdd1f42ae1..36331eee6e 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -631,7 +631,7 @@ buf_T *find_buffer_by_handle(Buffer buffer, Error *err)
   buf_T *rv = handle_get_buffer(buffer);
 
   if (!rv) {
-    api_set_error(err, kErrorTypeValidation, "Invalid buffer id");
+    api_set_error(err, kErrorTypeValidation, "Invalid buffer id: %d", buffer);
   }
 
   return rv;
@@ -646,7 +646,7 @@ win_T *find_window_by_handle(Window window, Error *err)
   win_T *rv = handle_get_window(window);
 
   if (!rv) {
-    api_set_error(err, kErrorTypeValidation, "Invalid window id");
+    api_set_error(err, kErrorTypeValidation, "Invalid window id: %d", window);
   }
 
   return rv;
@@ -661,7 +661,7 @@ tabpage_T *find_tab_by_handle(Tabpage tabpage, Error *err)
   tabpage_T *rv = handle_get_tabpage(tabpage);
 
   if (!rv) {
-    api_set_error(err, kErrorTypeValidation, "Invalid tabpage id");
+    api_set_error(err, kErrorTypeValidation, "Invalid tabpage id: %d", tabpage);
   }
 
   return rv;
diff --git a/test/functional/api/tabpage_spec.lua b/test/functional/api/tabpage_spec.lua
index ed7ce72597..20b3163d95 100644
--- a/test/functional/api/tabpage_spec.lua
+++ b/test/functional/api/tabpage_spec.lua
@@ -24,6 +24,10 @@ describe('api/tabpage', function()
       nvim('set_current_win', win3)
       eq(win3, tabpage('get_win', tab2))
     end)
+
+    it('validates args', function()
+      eq('Invalid tabpage id: 23', pcall_err(tabpage, 'list_wins', 23))
+    end)
   end)
 
   describe('{get,set,del}_var', function()
diff --git a/test/functional/api/window_spec.lua b/test/functional/api/window_spec.lua
index 17e0d3235c..8c7c3208c0 100644
--- a/test/functional/api/window_spec.lua
+++ b/test/functional/api/window_spec.lua
@@ -55,8 +55,8 @@ describe('API/win', function()
     end)
 
     it('validates args', function()
-      eq('Invalid buffer id', pcall_err(window, 'set_buf', nvim('get_current_win'), 23))
-      eq('Invalid window id', pcall_err(window, 'set_buf', 23, nvim('get_current_buf')))
+      eq('Invalid buffer id: 23', pcall_err(window, 'set_buf', nvim('get_current_win'), 23))
+      eq('Invalid window id: 23', pcall_err(window, 'set_buf', 23, nvim('get_current_buf')))
     end)
   end)
 
@@ -73,7 +73,7 @@ describe('API/win', function()
 
     it('does not leak memory when using invalid window ID with invalid pos',
     function()
-      eq('Invalid window id', pcall_err(meths.win_set_cursor, 1, {"b\na"}))
+      eq('Invalid window id: 1', pcall_err(meths.win_set_cursor, 1, {"b\na"}))
     end)
 
     it('updates the screen, and also when the window is unfocused', function()
diff --git a/test/functional/autocmd/autocmd_spec.lua b/test/functional/autocmd/autocmd_spec.lua
index 805db9dd78..43534c9e7e 100644
--- a/test/functional/autocmd/autocmd_spec.lua
+++ b/test/functional/autocmd/autocmd_spec.lua
@@ -219,7 +219,7 @@ describe('autocmd', function()
     eq(7, eval('g:test'))
 
     -- API calls are blocked when aucmd_win is not in scope
-    eq('Vim(call):E5555: API call: Invalid window id',
+    eq('Vim(call):E5555: API call: Invalid window id: 1001',
       pcall_err(command, "call nvim_set_current_win(g:winid)"))
 
     -- second time aucmd_win is needed, a different code path is invoked
@@ -257,7 +257,7 @@ describe('autocmd', function()
     eq(0, eval('g:had_value'))
     eq(7, eval('g:test'))
 
-    eq('Vim(call):E5555: API call: Invalid window id',
+    eq('Vim(call):E5555: API call: Invalid window id: 1001',
       pcall_err(command, "call nvim_set_current_win(g:winid)"))
   end)
 
diff --git a/test/functional/eval/api_functions_spec.lua b/test/functional/eval/api_functions_spec.lua
index f527aff33f..ccd97fc8c7 100644
--- a/test/functional/eval/api_functions_spec.lua
+++ b/test/functional/eval/api_functions_spec.lua
@@ -44,7 +44,7 @@ describe('eval-API', function()
     eq('Vim(call):E5555: API call: Wrong type for argument 1, expecting Buffer', err)
 
     err = exc_exec('call nvim_buf_line_count(17)')
-    eq('Vim(call):E5555: API call: Invalid buffer id', err)
+    eq('Vim(call):E5555: API call: Invalid buffer id: 17', err)
   end)
 
 
diff --git a/test/functional/lua/api_spec.lua b/test/functional/lua/api_spec.lua
index 23167d3ed9..896554f7a3 100644
--- a/test/functional/lua/api_spec.lua
+++ b/test/functional/lua/api_spec.lua
@@ -39,7 +39,7 @@ describe('luaeval(vim.api.…)', function()
       eq({false, 'Argument "pos" must be a [row, col] array'},
          funcs.luaeval('{pcall(vim.api.nvim_win_set_cursor, 0, {1, 2, 3})}'))
       -- Used to produce a memory leak due to a bug in nvim_win_set_cursor
-      eq({false, 'Invalid window id'},
+      eq({false, 'Invalid window id: -1'},
          funcs.luaeval('{pcall(vim.api.nvim_win_set_cursor, -1, {1, 2, 3})}'))
     end)
 
diff --git a/test/functional/lua/commands_spec.lua b/test/functional/lua/commands_spec.lua
index 96eaa7991b..cbc3aee557 100644
--- a/test/functional/lua/commands_spec.lua
+++ b/test/functional/lua/commands_spec.lua
@@ -47,7 +47,7 @@ describe(':lua command', function()
        pcall_err(command, 'lua ()'))
     eq([[Vim(lua):E5108: Error executing lua [string ":lua"]:1: TEST]],
        exc_exec('lua error("TEST")'))
-    eq([[Vim(lua):E5108: Error executing lua [string ":lua"]:1: Invalid buffer id]],
+    eq([[Vim(lua):E5108: Error executing lua [string ":lua"]:1: Invalid buffer id: -10]],
        exc_exec('lua vim.api.nvim_buf_set_lines(-10, 1, 1, false, {"TEST"})'))
     eq({''}, curbufmeths.get_lines(0, 100, false))
   end)