diff --git a/similar/main/inferno.cpp b/similar/main/inferno.cpp
index bae16f6a6..10c701be3 100644
--- a/similar/main/inferno.cpp
+++ b/similar/main/inferno.cpp
@@ -408,7 +408,7 @@ d_interface_unique_state::d_interface_unique_state()
 void d_interface_unique_state::update_window_title()
 {
 #if SDL_MAJOR_VERSION == 1
-	if (!PilotName[0])
+	if (!PilotName[0u])
 		SDL_WM_SetCaption(DESCENT_VERSION, DXX_SDL_WINDOW_CAPTION);
 	else
 	{
diff --git a/similar/main/menu.cpp b/similar/main/menu.cpp
index 7be0d4ad5..83ffab8eb 100644
--- a/similar/main/menu.cpp
+++ b/similar/main/menu.cpp
@@ -384,7 +384,7 @@ static void RegisterPlayer()
 	int allow_abort_flag = 1;
 
 	auto &callsign = InterfaceUniqueState.PilotName;
-	if (!callsign[0])
+	if (!callsign[0u])
 	{
 		if (!*static_cast<const char *>(GameCfg.LastPlayer))
 		{
@@ -474,7 +474,7 @@ static int main_menu_handler(newmenu *menu,const d_event &event, int *menu_choic
 	switch (event.type)
 	{
 		case EVENT_WINDOW_CREATED:
-			if (InterfaceUniqueState.PilotName[0])
+			if (InterfaceUniqueState.PilotName[0u])
 				break;
 			RegisterPlayer();
 			break;