diff --git a/src/complete.cpp b/src/complete.cpp
index fccf7016c..266df99fe 100644
--- a/src/complete.cpp
+++ b/src/complete.cpp
@@ -1362,12 +1362,19 @@ void completer_t::escape_opening_brackets(const wcstring &argument) {
     bool escaped = false;
     for (wchar_t c : argument) {
         have_unquoted_unescaped_bracket |= (c == L'[') && !quote && !escaped;
-        if (quote) {
-            if (c == quote && !escaped) quote = L'\0';
-        } else {
-            if ((c == L'\'' || c == L'"') && !escaped) quote = c;
+        if (escaped) {
+            escaped = false;
+        } else if (c == L'\\') {
+            escaped = true;
+        } else if (c == L'\'' || c == L'"') {
+            if (quote == c) {
+                // Closing a quote.
+                quote = L'\0';
+            } else if (quote == L'\0') {
+                // Opening a quote.
+                quote = c;
+            }
         }
-        escaped = c == L'\\';
     }
     if (!have_unquoted_unescaped_bracket) return;
     // Since completion_apply_to_command_line will escape the completion, we need to provide an
diff --git a/src/fish_tests.cpp b/src/fish_tests.cpp
index 7c20ff49c..3b3c045f9 100644
--- a/src/fish_tests.cpp
+++ b/src/fish_tests.cpp
@@ -2619,6 +2619,8 @@ static void test_complete() {
 
     if (system("mkdir -p 'test/complete_test'")) err(L"mkdir failed");
     if (system("touch 'test/complete_test/has space'")) err(L"touch failed");
+    if (system("touch 'test/complete_test/bracket[abc]'")) err(L"touch failed");
+    if (system(R"(touch 'test/complete_test/gnarlybracket\[abc]')")) err(L"touch failed");
     if (system("touch 'test/complete_test/testfile'")) err(L"touch failed");
     if (system("chmod 700 'test/complete_test/testfile'")) err(L"chmod failed");
 
@@ -2643,6 +2645,33 @@ static void test_complete() {
     do_test(completions.size() == 1);
     do_test(completions.at(0).completion == L"space");
 
+    // Brackets - see #5831
+    completions.clear();
+    complete(L"echo (ls test/complete_test/bracket[", &completions, {}, vars, parser);
+    do_test(completions.size() == 1);
+    fprintf(stderr, "sup: %ls\n", completions.front().completion.c_str());
+    do_test(completions.at(0).completion == L"test/complete_test/bracket[abc]");
+
+    wcstring cmdline = L"touch test/complete_test/bracket[";
+    completions.clear();
+    complete(cmdline, &completions, {}, vars, parser);
+    do_test(completions.size() == 1);
+    do_test(completions.front().completion == L"test/complete_test/bracket[abc]");
+    size_t where = cmdline.size();
+    wcstring newcmdline = completion_apply_to_command_line(
+        completions.front().completion, completions.front().flags, cmdline, &where, false);
+    do_test(newcmdline == L"touch test/complete_test/bracket\\[abc\\] ");
+
+    completions.clear();
+    cmdline = LR"(touch test/complete_test/gnarlybracket\\[)";
+    complete(cmdline, &completions, {}, vars, parser);
+    do_test(completions.size() == 1);
+    do_test(completions.front().completion == LR"(test/complete_test/gnarlybracket\[abc])");
+    where = cmdline.size();
+    newcmdline = completion_apply_to_command_line(
+        completions.front().completion, completions.front().flags, cmdline, &where, false);
+    do_test(newcmdline == LR"(touch test/complete_test/gnarlybracket\\\[abc\] )");
+
     // Add a function and test completing it in various ways.
     // Note we're depending on function_data_t not complaining when given missing parsed_source /
     // body_node.