diff --git a/autoload/ale/completion.vim b/autoload/ale/completion.vim
index 5c054dd7..7b3a0e82 100644
--- a/autoload/ale/completion.vim
+++ b/autoload/ale/completion.vim
@@ -432,6 +432,11 @@ function! s:GetLSPCompletions(linter) abort
     let l:root = l:lsp_details.project_root
 
     function! OnReady(...) abort closure
+        " If we have sent a completion request already, don't send another.
+        if b:ale_completion_info.request_id
+            return
+        endif
+
         let l:Callback = a:linter.lsp is# 'tsserver'
         \   ? function('ale#completion#HandleTSServerResponse')
         \   : function('ale#completion#HandleLSPResponse')
diff --git a/test/completion/test_lsp_completion_messages.vader b/test/completion/test_lsp_completion_messages.vader
index 30a9c8e1..ed0f358b 100644
--- a/test/completion/test_lsp_completion_messages.vader
+++ b/test/completion/test_lsp_completion_messages.vader
@@ -15,7 +15,7 @@ Before:
   let g:message_list = []
   let g:capability_checked = ''
   let g:Callback = ''
-  let g:WaitCallback = v:null
+  let g:wait_callback_list = []
 
   function! ale#lsp_linter#StartLSP(buffer, linter) abort
     let l:conn = ale#lsp#NewConnection({})
@@ -37,7 +37,7 @@ Before:
 
   function! ale#lsp#WaitForCapability(conn_id, project_root, capability, callback) abort
     let g:capability_checked = a:capability
-    let g:WaitCallback = a:callback
+    call add(g:wait_callback_list, a:callback)
   endfunction
 
   function! ale#lsp#RegisterCallback(conn_id, callback) abort
@@ -47,6 +47,8 @@ Before:
   " Replace the Send function for LSP, so we can monitor calls to it.
   function! ale#lsp#Send(conn_id, message, ...) abort
     call add(g:message_list, a:message)
+
+    return 1
   endfunction
 
 After:
@@ -54,7 +56,7 @@ After:
 
   unlet! g:message_list
   unlet! g:capability_checked
-  unlet! g:WaitCallback
+  unlet! g:wait_callback_list
   unlet! g:Callback
   unlet! b:ale_old_omnifunc
   unlet! b:ale_old_completopt
@@ -98,9 +100,9 @@ Execute(The right message should be sent for the initial tsserver request):
   " We shouldn't register the callback yet.
   AssertEqual '''''', string(g:Callback)
 
-  AssertEqual type(function('type')), type(g:WaitCallback)
+  AssertEqual 1, len(g:wait_callback_list)
   AssertEqual 'completion', g:capability_checked
-  call call(g:WaitCallback, [347, '/foo/bar'])
+  call map(g:wait_callback_list, 'v:val([347, ''/foo/bar''])')
 
   " We should send the right callback.
   AssertEqual
@@ -114,9 +116,9 @@ Execute(The right message should be sent for the initial tsserver request):
   AssertEqual
   \ {
   \   'line_length': 3,
-  \   'conn_id': 0,
+  \   'conn_id': 347,
   \   'column': 3,
-  \   'request_id': 0,
+  \   'request_id': 1,
   \   'line': 1,
   \   'prefix': 'fo',
   \ },
@@ -185,9 +187,9 @@ Execute(The right message should be sent for the initial LSP request):
   " We shouldn't register the callback yet.
   AssertEqual '''''', string(g:Callback)
 
-  AssertEqual type(function('type')), type(g:WaitCallback)
+  AssertEqual 1, len(g:wait_callback_list)
   AssertEqual 'completion', g:capability_checked
-  call call(g:WaitCallback, [347, '/foo/bar'])
+  call map(g:wait_callback_list, 'v:val([347, ''/foo/bar''])')
 
   " We should send the right callback.
   AssertEqual
@@ -217,10 +219,58 @@ Execute(The right message should be sent for the initial LSP request):
   AssertEqual
   \ {
   \   'line_length': 3,
-  \   'conn_id': 0,
+  \   'conn_id': 347,
   \   'column': 3,
-  \   'request_id': 0,
+  \   'request_id': 1,
   \   'line': 1,
   \   'prefix': 'fo',
+  \   'completion_filter': 'ale#completion#python#CompletionItemFilter',
   \ },
   \ get(b:, 'ale_completion_info', {})
+
+Execute(Two completion requests shouldn't be sent in a row):
+  call ale#linter#PreventLoading('python')
+  call ale#linter#Define('python', {
+  \   'name': 'foo',
+  \   'lsp': 'stdio',
+  \   'executable': 'foo',
+  \   'command': 'foo',
+  \   'project_root_callback': {-> '/foo/bar'},
+  \})
+  call ale#linter#Define('python', {
+  \   'name': 'bar',
+  \   'lsp': 'stdio',
+  \   'executable': 'foo',
+  \   'command': 'foo',
+  \   'project_root_callback': {-> '/foo/bar'},
+  \})
+  let b:ale_linters = ['foo', 'bar']
+
+  " The cursor position needs to match what was saved before.
+  call setpos('.', [bufnr(''), 1, 5, 0])
+
+  call ale#completion#GetCompletions()
+
+  " We shouldn't register the callback yet.
+  AssertEqual '''''', string(g:Callback)
+
+  AssertEqual 2, len(g:wait_callback_list)
+  AssertEqual 'completion', g:capability_checked
+  call map(g:wait_callback_list, 'v:val([347, ''/foo/bar''])')
+
+  " We should only send one completion message for two LSP servers.
+  AssertEqual
+  \ [
+  \   [1, 'textDocument/didChange', {
+  \     'textDocument': {
+  \         'uri': ale#path#ToURI(expand('%:p')),
+  \         'version': g:ale_lsp_next_version_id - 1,
+  \     },
+  \     'contentChanges': [{'text': join(getline(1, '$'), "\n") . "\n"}]
+  \   }],
+  \   [0, 'textDocument/completion', {
+  \   'textDocument': {'uri': ale#path#ToURI(expand('%:p'))},
+  \   'position': {'line': 0, 'character': 3},
+  \   }],
+  \ ],
+  \ g:message_list