diff --git a/CHANGELOG.md b/CHANGELOG.md
index fc5ca5edc..b0a352055 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,7 @@
 - Minor: Don't show update button for nightly builds on macOS and Linux, this was already the case for Windows (#2163, #2164)
 - Minor: Tab and split titles now use display/localized channel names (#2189)
 - Minor: Add a setting to limit the amount of historical messages loaded from the Recent Messages API (#2250, #2252)
+- Minor: Made username autocompletion truecase (#1199, #1883)
 - Bugfix: Fix crash occurring when pressing Escape in the Color Picker Dialog (#1843)
 - Bugfix: Fix bug where the "check user follow state" event could trigger a network request requesting the user to follow or unfollow a user. By itself its quite harmless as it just repeats to Twitch the same follow state we had, so no follows should have been lost by this but it meant there was a rogue network request that was fired that could cause a crash (#1906)
 - Bugfix: /usercard command will now respect the "Automatically close user popup" setting (#1918)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 29094f702..de20932b0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,6 +37,9 @@ if (BUILD_TESTS)
 
     target_link_libraries(chatterino-test PajladaSerialize)
 
+    set_property(TARGET chatterino-test PROPERTY CXX_STANDARD 17)
+    set_property(TARGET chatterino-test PROPERTY CXX_STANDARD_REQUIRED ON)
+
     gtest_discover_tests(chatterino-test)
 else()
     message(FATAL_ERROR "This cmake file is only intended for tests right now. Use qmake to build chatterino2")
diff --git a/src/common/ChannelChatters.cpp b/src/common/ChannelChatters.cpp
index 4728aef94..3657aeeec 100644
--- a/src/common/ChannelChatters.cpp
+++ b/src/common/ChannelChatters.cpp
@@ -67,7 +67,7 @@ void ChannelChatters::addPartedUser(const QString &user)
 
 void ChannelChatters::setChatters(UsernameSet &&set)
 {
-    *this->chatters_.access() = set;
+    this->chatters_.access()->merge(std::move(set));
 }
 
 const QColor ChannelChatters::getUserColor(const QString &user)
diff --git a/src/common/UsernameSet.cpp b/src/common/UsernameSet.cpp
index 958a6fc3a..1c0474e93 100644
--- a/src/common/UsernameSet.cpp
+++ b/src/common/UsernameSet.cpp
@@ -4,6 +4,30 @@
 
 namespace chatterino {
 
+namespace {
+
+    std::pair<UsernameSet::Iterator, bool> findOrErase(
+        std::set<QString, CaseInsensitiveLess> &set, const QString &value)
+    {
+        if (!value.isLower())
+        {
+            auto iter = set.find(value);
+            if (iter != set.end())
+            {
+                if (QString::compare(*iter, value, Qt::CaseSensitive) != 0)
+                {
+                    set.erase(iter);
+                }
+                else
+                {
+                    return {iter, false};
+                }
+            }
+        }
+        return {set.end(), true};
+    }
+}  // namespace
+
 //
 // UsernameSet
 //
@@ -43,15 +67,25 @@ std::set<QString>::size_type UsernameSet::size() const
 
 std::pair<UsernameSet::Iterator, bool> UsernameSet::insert(const QString &value)
 {
-    this->insertPrefix(value);
+    auto pair = findOrErase(this->items, value);
+    if (!pair.second)
+    {
+        return pair;
+    }
 
+    this->insertPrefix(value);
     return this->items.insert(value);
 }
 
 std::pair<UsernameSet::Iterator, bool> UsernameSet::insert(QString &&value)
 {
-    this->insertPrefix(value);
+    auto pair = findOrErase(this->items, value);
+    if (!pair.second)
+    {
+        return pair;
+    }
 
+    this->insertPrefix(value);
     return this->items.insert(std::move(value));
 }
 
@@ -68,6 +102,24 @@ bool UsernameSet::contains(const QString &value) const
     return this->items.count(value) == 1;
 }
 
+void UsernameSet::merge(UsernameSet &&set)
+{
+    for (auto it = this->items.begin(); it != this->items.end();)
+    {
+        auto iter = set.items.find(*it);
+        if (iter == set.items.end())
+        {
+            it = this->items.erase(it);
+        }
+        else
+        {
+            ++it;
+        }
+    }
+    this->items.merge(set.items);
+    this->firstKeyForPrefix = set.firstKeyForPrefix;
+}
+
 //
 // Range
 //
diff --git a/src/common/UsernameSet.hpp b/src/common/UsernameSet.hpp
index f43916cc4..1268695ee 100644
--- a/src/common/UsernameSet.hpp
+++ b/src/common/UsernameSet.hpp
@@ -77,6 +77,7 @@ public:
     std::pair<Iterator, bool> insert(QString &&value);
 
     bool contains(const QString &value) const;
+    void merge(UsernameSet &&set);
 
 private:
     void insertPrefix(const QString &string);
diff --git a/src/providers/twitch/TwitchChannel.cpp b/src/providers/twitch/TwitchChannel.cpp
index 5b3029690..ce75e02fa 100644
--- a/src/providers/twitch/TwitchChannel.cpp
+++ b/src/providers/twitch/TwitchChannel.cpp
@@ -804,6 +804,7 @@ void TwitchChannel::fetchDisplayName()
                                               .arg(channel->getName())
                                               .arg(user.displayName));
             }
+            channel->addRecentChatter(channel->getDisplayName());
             channel->displayNameChanged.invoke();
         },
         [] {});
diff --git a/tests/src/UsernameSet.cpp b/tests/src/UsernameSet.cpp
index 7098941bf..fad210520 100644
--- a/tests/src/UsernameSet.cpp
+++ b/tests/src/UsernameSet.cpp
@@ -44,17 +44,40 @@ TEST(UsernameSet, insert)
 
     EXPECT_EQ(set.size(), 1);
 
+    // Non-lowercase variant should override full lowercase variant
+    p = set.insert("PAJLADA");
+    EXPECT_TRUE(p.second);
+
+    EXPECT_EQ(set.size(), 1);
+
+    // Lowercase variant should not override non-lowercase variant
+    p = set.insert("pajlada");
+    EXPECT_FALSE(p.second);
+
+    EXPECT_EQ(set.size(), 1);
+
     p = set.insert("pajbot");
     EXPECT_TRUE(p.second);
 
     EXPECT_EQ(set.size(), 2);
 
-    p = set.insert("pajlada");
+    p = set.insert("pajbot");
     EXPECT_FALSE(p.second);
 
     EXPECT_EQ(set.size(), 2);
 
-    p = set.insert("PAJLADA");
+    p = set.insert("Pajbot");
+    EXPECT_TRUE(p.second);
+
+    EXPECT_EQ(set.size(), 2);
+
+    p = set.insert("PAJBOT");
+    EXPECT_TRUE(p.second);
+
+    EXPECT_EQ(set.size(), 2);
+
+    // Same uppercase should not result in a change
+    p = set.insert("PAJBOT");
     EXPECT_FALSE(p.second);
 
     EXPECT_EQ(set.size(), 2);