diff --git a/cassandane/tiny-tests/JMAPEmail/email_query_cjk_fullwidth b/cassandane/tiny-tests/JMAPEmail/email_query_cjk_fullwidth
new file mode 100644
index 0000000000..b1529f637b
--- /dev/null
+++ b/cassandane/tiny-tests/JMAPEmail/email_query_cjk_fullwidth
@@ -0,0 +1,70 @@
+#!perl
+use Cassandane::Tiny;
+
+sub test_email_query_cjk_fullwidth
+    :min_version_3_9 :needs_component_jmap :JMAPExtensions
+{
+    my ($self) = @_;
+    my $jmap = $self->{jmap};
+
+use utf8;
+    my $res = $jmap->CallMethods([
+        ['Email/set', {
+            create => {
+                email1 => {
+                    mailboxIds => {
+                        '$inbox' => JSON::true
+                    },
+                    from => [{ email => 'foo@local' }],
+                    to => [{ email => 'bar@local' }],
+                    subject => $_->{id},
+                    bodyStructure => {
+                        type => 'text/plain',
+                        partId => 'part1',
+                    },
+                    bodyValues => {
+                        part1 => {
+                            value =>  <<'EOF'
+三菱ＵＦＪファクター株式会社
+EOF
+                        },
+                    },
+                },
+            },
+        }, 'R1'],
+    ]);
+    my $email1Id = $res->[0][1]{created}{email1}{id};
+    $self->assert_not_null($email1Id);
+
+    xlog $self, "run squatter";
+    $self->{instance}->run_command({cyrus => 1}, 'squatter');
+
+    my $res = $jmap->CallMethods([
+        ['Email/query', {
+            filter => {
+                body => "ＵＦＪ",
+            },
+        }, 'R1'],
+        ['Email/query', {
+            filter => {
+                body => "三菱ＵＦＪファクター株式会社",
+            },
+        }, 'R2'],
+        ['Email/query', {
+            filter => {
+                body => "三菱ＵＦＪ",
+            },
+        }, 'R3'],
+        ['Email/query', {
+            filter => {
+                body => "三菱",
+            },
+        }, 'R4'],
+    ]);
+    $self->assert_deep_equals([$email1Id], $res->[0][1]{ids});
+    $self->assert_deep_equals([$email1Id], $res->[1][1]{ids});
+    $self->assert_deep_equals([$email1Id], $res->[2][1]{ids});
+    $self->assert_deep_equals([$email1Id], $res->[3][1]{ids});
+
+no utf8;
+}
diff --git a/imap/xapian_wrap.cpp b/imap/xapian_wrap.cpp
index eae11b563d..010184bc62 100644
--- a/imap/xapian_wrap.cpp
+++ b/imap/xapian_wrap.cpp
@@ -720,24 +720,30 @@ struct xapian_dbw
     std::vector<std::string> *subjects;
 };
 
-
-static int xapian_dbw_init(xapian_dbw_t *dbw)
+static Xapian::TermGenerator *new_term_generator(void)
 {
-    dbw->default_stemmer = new Xapian::Stem(new CyrusSearchStemmer);
-    dbw->default_stopper = get_stopper("en");
-    dbw->term_generator = new Xapian::TermGenerator;
-    dbw->term_generator->set_max_word_length(XAPIAN_MAX_TERM_LENGTH);
+    auto termgen = new Xapian::TermGenerator;
+    termgen->set_max_word_length(XAPIAN_MAX_TERM_LENGTH);
     /* Always enable CJK word tokenization */
 #if defined(USE_XAPIAN_WORD_BREAKS)
-    dbw->term_generator->set_flags(Xapian::TermGenerator::FLAG_WORD_BREAKS,
+    termgen->set_flags(Xapian::TermGenerator::FLAG_WORD_BREAKS,
             ~Xapian::TermGenerator::FLAG_WORD_BREAKS);
 #elif defined(USE_XAPIAN_CJK_WORDS)
-    dbw->term_generator->set_flags(Xapian::TermGenerator::FLAG_CJK_WORDS,
+    termgen->set_flags(Xapian::TermGenerator::FLAG_CJK_WORDS,
             ~Xapian::TermGenerator::FLAG_CJK_WORDS);
 #else
-    dbw->term_generator->set_flags(Xapian::TermGenerator::FLAG_CJK_NGRAM,
+    termgen->set_flags(Xapian::TermGenerator::FLAG_CJK_NGRAM,
             ~Xapian::TermGenerator::FLAG_CJK_NGRAM);
 #endif
+    return termgen;
+}
+
+
+static int xapian_dbw_init(xapian_dbw_t *dbw)
+{
+    dbw->default_stemmer = new Xapian::Stem(new CyrusSearchStemmer);
+    dbw->default_stopper = get_stopper("en");
+    dbw->term_generator = new_term_generator();
     dbw->doclangs = new std::set<std::string>;
     dbw->subjects = new std::vector<std::string>;
     return 0;
@@ -1868,6 +1874,52 @@ static Xapian::Query *query_new_type(const xapian_db_t *db __attribute__((unused
     return new Xapian::Query(q);
 }
 
+static Xapian::Query* xapian_query_new_match_cjk(const xapian_db_t *db, const char *str, const char *prefix)
+{
+    Xapian::Query *q = new Xapian::Query {db->parser->parse_query(
+            str,
+#if defined(USE_XAPIAN_WORD_BREAKS)
+            Xapian::QueryParser::FLAG_WORD_BREAKS,
+#elif defined(USE_XAPIAN_CJK_WORDS)
+            Xapian::QueryParser::FLAG_CJK_WORDS,
+#else
+            Xapian::QueryParser::FLAG_CJK_NGRAM,
+#endif
+            prefix)};
+
+#if defined(USE_XAPIAN_WORD_BREAKS) || defined(USE_XAPIAN_CJK_WORDS)
+    // There is a bug in Xapian v1.5 and CJK word segmentation, in which
+    // a term starting with a fullwidth Latin character such as U+FF21
+    // is indexed with capitalization, but queried in small letter form
+    // when parsed with parse_query.
+    //
+    // As a workaround, the following code checks if the query string
+    // contains any characters in the Halfwidth and Fullwidth Forms
+    // Unicode block. If so, it queries for either the query as
+    // generated by the query parser, or the terms as generated during
+    // indexing.
+    //
+    // XXX this should better be handled by normalizing characters in
+    // that Unicode block during indexing.
+    for (auto it = Xapian::Utf8Iterator(str); it != Xapian::Utf8Iterator(); ++it) {
+        if (*it >= 0xff00 && *it <= 0xffef) {
+            Xapian::TermGenerator *termgen = new_term_generator();
+            Xapian::Document doc;
+            termgen->set_document(doc);
+            termgen->index_text(str, 1, prefix);
+            Xapian::Query qq{Xapian::Query::OP_AND, doc.termlist_begin(), doc.termlist_end()};
+            if (qq.get_length()) {
+                *q |= qq;
+            }
+            delete termgen;
+            break; // stop at first occurence of full/half-width character
+        }
+    }
+#endif
+
+    return q;
+}
+
 EXPORTED Xapian::Query *
 xapian_query_new_match_internal(const xapian_db_t *db, int partnum, const char *str)
 {
@@ -1898,16 +1950,7 @@ xapian_query_new_match_internal(const xapian_db_t *db, int partnum, const char *
         // Don't stem queries for Thaana codepage (0780) or higher.
         for (const unsigned char *p = (const unsigned char *)str; *p; p++) {
             if (*p > 221) //has highbit
-                return new Xapian::Query {db->parser->parse_query(
-                    str,
-#if defined(USE_XAPIAN_WORD_BREAKS)
-                    Xapian::QueryParser::FLAG_WORD_BREAKS,
-#elif defined(USE_XAPIAN_CJK_WORDS)
-                    Xapian::QueryParser::FLAG_CJK_WORDS,
-#else
-                    Xapian::QueryParser::FLAG_CJK_NGRAM,
-#endif
-                    prefix)};
+                return xapian_query_new_match_cjk(db, str, prefix);
         }
 
         // Stemable codepage.