diff --git a/src/core/Tools.cpp b/src/core/Tools.cpp
index 09938b82a..46cde95bc 100644
--- a/src/core/Tools.cpp
+++ b/src/core/Tools.cpp
@@ -205,7 +205,7 @@ namespace Tools
 
     bool isBase64(const QByteArray& ba)
     {
-        constexpr auto pattern = R"(^(?:[a-z0-9+]{4})*(?:[a-z0-9+]{3}=|[a-z0-9+]{2}==)?$)";
+        constexpr auto pattern = R"(^(?:[a-z0-9+/]{4})*(?:[a-z0-9+/]{3}=|[a-z0-9+/]{2}==)?$)";
         QRegExp regexp(pattern, Qt::CaseInsensitive, QRegExp::RegExp2);
 
         QString base64 = QString::fromLatin1(ba.constData(), ba.size());
diff --git a/tests/TestTools.cpp b/tests/TestTools.cpp
index de5a80c0a..100eb6306 100644
--- a/tests/TestTools.cpp
+++ b/tests/TestTools.cpp
@@ -59,6 +59,7 @@ void TestTools::testIsBase64()
     QVERIFY(Tools::isBase64(QByteArray("12==")));
     QVERIFY(Tools::isBase64(QByteArray("abcd9876MN==")));
     QVERIFY(Tools::isBase64(QByteArray("abcd9876DEFGhijkMNO=")));
+    QVERIFY(Tools::isBase64(QByteArray("abcd987/DEFGh+jk/NO=")));
     QVERIFY(not Tools::isBase64(QByteArray("abcd123==")));
     QVERIFY(not Tools::isBase64(QByteArray("abc_")));
     QVERIFY(not Tools::isBase64(QByteArray("123")));