diff --git a/src/compat/glibcxx_sanity.cpp b/src/compat/glibcxx_sanity.cpp
index 18d990c60..419d751cd 100644
--- a/src/compat/glibcxx_sanity.cpp
+++ b/src/compat/glibcxx_sanity.cpp
@@ -1,62 +1,62 @@
 // Copyright (c) 2009-2014 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <list>
 #include <locale>
 #include <stdexcept>
 
 namespace {
 // trigger: use ctype<char>::widen to trigger ctype<char>::_M_widen_init().
 // test: convert a char from narrow to wide and back. Verify that the result
 //   matches the original.
 bool sanity_test_widen(char testchar) {
     const std::ctype<char> &test(
         std::use_facet<std::ctype<char>>(std::locale()));
     return test.narrow(test.widen(testchar), 'b') == testchar;
 }
 
 // trigger: use list::push_back and list::pop_back to trigger _M_hook and
 //   _M_unhook.
 // test: Push a sequence of integers into a list. Pop them off and verify that
 //   they match the original sequence.
 bool sanity_test_list(unsigned int size) {
     std::list<unsigned int> test;
     for (unsigned int i = 0; i != size; ++i) {
         test.push_back(i + 1);
     }
 
     if (test.size() != size) {
         return false;
     }
 
     while (!test.empty()) {
         if (test.back() != test.size()) {
             return false;
         }
         test.pop_back();
     }
     return true;
 }
 
 } // namespace
 
 // trigger: string::at(x) on an empty string to trigger
 // __throw_out_of_range_fmt.
 // test: force std::string to throw an out_of_range exception. Verify that
 //   it's caught correctly.
 bool sanity_test_range_fmt() {
     std::string test;
     try {
-        test.at(1);
+        [[maybe_unused]] auto &c = test.at(1);
     } catch (const std::out_of_range &) {
         return true;
     } catch (...) {
     }
     return false;
 }
 
 bool glibcxx_sanity_test() {
     return sanity_test_widen('a') && sanity_test_list(100) &&
            sanity_test_range_fmt();
 }