diff --git a/src/lib/server/Server.cpp b/src/lib/server/Server.cpp
index f9040026f..b55cdb73d 100644
--- a/src/lib/server/Server.cpp
+++ b/src/lib/server/Server.cpp
@@ -2065,8 +2065,11 @@ Server::removeClient(BaseClientProxy* client)
 void
 Server::closeClient(BaseClientProxy* client, const char* msg)
 {
-	assert(client != m_primaryClient);
-	assert(msg != nullptr);
+       assert(client != m_primaryClient);
+       if (msg == nullptr) {
+               LOG_ERR("closeClient called with null msg");
+               return;
+       }
 
 	// send message to client.  this message should cause the client
 	// to disconnect.  we add this client to the closed client list
diff --git a/src/test/unittests/server/CloseClientTests.cpp b/src/test/unittests/server/CloseClientTests.cpp
new file mode 100644
index 000000000..cdf790e4c
--- /dev/null
+++ b/src/test/unittests/server/CloseClientTests.cpp
@@ -0,0 +1,80 @@
+#define INPUTLEAP_TEST_ENV
+#define NDEBUG
+
+#include <gtest/gtest.h>
+
+#include "server/Server.h"
+#include "server/ClientProxy.h"
+#include "server/IClientConnection.h"
+#include "base/EventTarget.h"
+#include "inputleap/Clipboard.h"
+#include "inputleap/option_types.h"
+
+namespace inputleap {
+
+class DummyConnection : public IClientConnection {
+public:
+    const EventTarget* get_event_target() override { return nullptr; }
+    IStream* get_stream() override { return nullptr; }
+    void send_query_info_1_6() override {}
+    void send_leave_1_6() override {}
+    void send_enter_1_6(std::int32_t, std::int32_t, std::uint32_t, KeyModifierMask) override {}
+    void send_key_down_1_6(KeyID, KeyModifierMask, KeyButton) override {}
+    void send_key_up_1_6(KeyID, KeyModifierMask, KeyButton) override {}
+    void send_key_repeat_1_6(KeyID, KeyModifierMask, std::int32_t, KeyButton) override {}
+    void send_mouse_down_1_6(ButtonID) override {}
+    void send_mouse_up_1_6(ButtonID) override {}
+    void send_mouse_move_1_6(std::int32_t, std::int32_t) override {}
+    void send_mouse_relative_move_1_6(std::int32_t, std::int32_t) override {}
+    void send_mouse_wheel_1_6(std::int32_t, std::int32_t) override {}
+    void send_drag_info_1_6(std::uint32_t, const std::string&) override {}
+    void send_screensaver_1_6(bool) override {}
+    void send_reset_options_1_6() override {}
+    void send_set_options_1_6(const OptionsList&) override {}
+    void send_info_ack_1_6() override {}
+    void send_keep_alive_1_6() override {}
+    void send_close_1_6(const char*) override {}
+    void send_clipboard_chunk_1_6(const ClipboardChunk&) override {}
+    void send_file_chunk_1_6(const FileChunk&) override {}
+    void send_grab_clipboard(ClipboardID) override {}
+    void flush() override {}
+    void close() override {}
+};
+
+class DummyClientProxy : public ClientProxy {
+public:
+    DummyClientProxy(const std::string& name, std::unique_ptr<IClientConnection> backend)
+        : ClientProxy(name, std::move(backend)) {}
+
+    bool getClipboard(ClipboardID, IClipboard*) const override { return false; }
+    void getShape(std::int32_t&, std::int32_t&, std::int32_t&, std::int32_t&) const override {}
+    void getCursorPos(std::int32_t&, std::int32_t&) const override {}
+    void enter(std::int32_t, std::int32_t, std::uint32_t, KeyModifierMask, bool) override {}
+    bool leave() override { return true; }
+    void setClipboard(ClipboardID, const IClipboard*) override {}
+    void grabClipboard(ClipboardID) override {}
+    void setClipboardDirty(ClipboardID, bool) override {}
+    void keyDown(KeyID, KeyModifierMask, KeyButton) override {}
+    void keyRepeat(KeyID, KeyModifierMask, std::int32_t, KeyButton) override {}
+    void keyUp(KeyID, KeyModifierMask, KeyButton) override {}
+    void mouseDown(ButtonID) override {}
+    void mouseUp(ButtonID) override {}
+    void mouseMove(std::int32_t, std::int32_t) override {}
+    void mouseRelativeMove(std::int32_t, std::int32_t) override {}
+    void mouseWheel(std::int32_t, std::int32_t) override {}
+    void screensaver(bool) override {}
+    void resetOptions() override {}
+    void setOptions(const OptionsList&) override {}
+    void sendDragInfo(std::uint32_t, const char*, size_t) override {}
+    void file_chunk_sending(const FileChunk&) override {}
+};
+
+TEST(ServerCloseClientTests, handles_null_message)
+{
+    Server server;
+    DummyClientProxy client("dummy", std::make_unique<DummyConnection>());
+    EXPECT_NO_THROW(server.closeClient(&client, nullptr));
+}
+
+} // namespace inputleap
+