diff --git a/Koha/SearchEngine/Elasticsearch/QueryBuilder.pm b/Koha/SearchEngine/Elasticsearch/QueryBuilder.pm
index 427b041ebe..e1299d74dd 100644
--- a/Koha/SearchEngine/Elasticsearch/QueryBuilder.pm
+++ b/Koha/SearchEngine/Elasticsearch/QueryBuilder.pm
@@ -47,6 +47,7 @@ use URI::Escape qw( uri_escape_utf8 );
 
 use C4::Context;
 use Koha::Exceptions;
+use Koha::Authority;
 use Koha::Caches;
 use Koha::AuthorisedValueCategories;
 
@@ -608,23 +609,9 @@ our $koha_to_index_name = {
     all                     => ''
 };
 
-# Note that sears and aat map to 008/11 values here
-# but don't appear in C4/Heading/MARC21 thesaurus
-# because they don't have values in controlled field indicators
-# https://www.loc.gov/marc/authority/ad008.html
-our $thesaurus_to_value = {
-    lcsh          => 'a',
-    lcac          => 'b',
-    mesh          => 'c',
-    nal           => 'd',
-    notapplicable => 'n',
-    cash          => 'k',
-    rvm           => 'v',
-    aat           => 'r',
-    sears         => 's',
-    notdefined    => 'z',
-    notspecified  => '|'
-};
+# Delegates to Koha::Authority's table so there is a single source of
+# truth for thesaurus-name -> 008/11-code (bug 31925).
+our $thesaurus_to_value = $Koha::Authority::MARC21_THESAURUS_TO_CONTROL_FIELD_008_11;
 
 sub build_authorities_query_compat {
     my (
diff --git a/t/db_dependent/Koha/SearchEngine/Elasticsearch/QueryBuilder.t b/t/db_dependent/Koha/SearchEngine/Elasticsearch/QueryBuilder.t
index d7b9528145..47ca31b883 100755
--- a/t/db_dependent/Koha/SearchEngine/Elasticsearch/QueryBuilder.t
+++ b/t/db_dependent/Koha/SearchEngine/Elasticsearch/QueryBuilder.t
@@ -85,7 +85,7 @@ $se->mock(
 
 subtest 'build_authorities_query_compat() tests' => sub {
 
-    plan tests => 81;
+    plan tests => 83;
 
     my $qb;
 
@@ -249,6 +249,24 @@ subtest 'build_authorities_query_compat() tests' => sub {
         "If mapping found for marclist the index is passed through converted"
     );
 
+    # Thesaurus value mapping delegates to Koha::Authority (bug 31925)
+    $query = $qb->build_authorities_query_compat(
+        ['thesaurus'], undef, undef, ['contains'], ['lcsh'], 'AUTH_TYPE',
+        'asc'
+    );
+    is(
+        $query->{query}->{bool}->{must}[0]->{query_string}->{query}, 'a*',
+        "thesaurus value 'lcsh' is still translated to 008/11 code 'a'"
+    );
+    $query = $qb->build_authorities_query_compat(
+        ['thesaurus'], undef, undef, ['contains'], ['mesh'], 'AUTH_TYPE',
+        'asc'
+    );
+    is(
+        $query->{query}->{bool}->{must}[0]->{query_string}->{query}, 'c*',
+        "thesaurus value 'mesh' is still translated to 008/11 code 'c'"
+    );
+
 };
 
 subtest 'build_query tests' => sub {