Sorry; This IS a kiCAD symbol.
It’s what I got searching for the 7404. I fully explained above.
The only one external library I have, is mine, but I have not the 7404 at all.
I have other stuff (INA163 for instance etc not these ICs at all)
Ah you modified a symbol from the older IEEE library that has hidden power pins instead of the current standard of a power unit. You did not tell us you had done this but in any case this led to you finding the error with the type assignment of pins. So it was worthwhile to query the anomaly.
If you want the usual triangular inverter use the 74LS04 symbol. In fact unless you are an antique junk, er chip, collector like me it’s more likely you have a LS or HC/T part rather than one from the original series. If you really do have the original 7404, just rename the chip name from 74LS04 to 7404 on the schematic.
I did tell.
As I said 7404 I got the squares :-/ from default library in kiCAD
HOwever I will follow your suggestion to implement the LS instead.
Those circles only show when the gate is placed on the schematic. They do not show in the symbol browser.
So: none of us are to blame…we can stick it all on the librarians; and @Piotr saved all our skins! 
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This appears to be an artifact for the IEEE family of symbols, which predate power units. Some of us have been there before.
I still fighting with the classical kiCAD issues …one day they will provide a solution for such 
Never popped up. Now it did it.
Bridge rectifiers: same issue (in another schematics)
I’m trying to decide if I can’t remember or don’t want to remember.
I do remember that I have some real 74xx (without all those letters) ICs somewhere out in the shed, just don’t ask me to find them. 
As you write ‘classical’ I understand you know that solution is to add PwrSource (not sure of name, as I’m not using it) symbols whenever needed.
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yes we wrote at the same time 
while I posted the screenshot.
I had also to fix the symbol of the bridge rectifier … ve/AC/ve/AC …
So follow my method - never, ever run ERC (don’t miss ERC with DRC as you missed it in your first post).
Sorry I just mistyped. I corrected it.
Some reading from the FAQs for you in case you bump into more ERC issues.
Unlike Piotr, some of us think ERC is useful, you just have to understand what it’s saying and when to use your own judgement.
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I earned my first real money in my live by designing and making a device that contained a lot of 74xx ICs. I was a student and got for it 2.5x my father month salary. The factory device doing the same cost 4x more. What I have done was chronocomparator - you put on its table the electronic watch and you see at its display how accurate is that watch (0.1s/day resolution). I made a quartz 1MHz generator. I used thermistor to stabilize temperature (BD139 was the heater). The generator was encased in polystyrene. Chronocomparator stabilized after about 15 minutes after being switched on. I found that after 8 hours it lost accuracy. The reason was the 74xx ICs give off a lot of heat and temperature inside whole case got higher than I set in generator. I made a lot of 5mm holes in wooden case of that and raised the generator temperature.
I don’t say it is not useful.
Years ago, I took over our PCB making from someone else. This person, telling what to do in turn, did not mention the existence of the ERC in Protel, and I only used what I needed and never found this function. When I decided to move to KiCad was the first time I noticed ERC, but found that to have 0 errors I have to add many symbols to my schematic I don’t like. So as I have been without an ERC for teen years I assumed it may continue to do so. Why many - because I use many ferrite beads in power lines and because I prefer continuous GND at bottom so it happens me to use 0Rs in power lines. Adding Power Flag after each of it has no sense to me.
Understood. But if I had a dollar for every time you write about avoiding ERC I could go buy a nice computer. 
If you ask for a dollar for every question about power inputs not driven by power output you could earn more, I believe. But I have to admit that not a lot more
I will try to hold back myself from writing this.
I don’t know if in V6 it will be possible to block that one Error. If so may be I will start to use ERC.
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What is ERC?
Not quite true… I do use it often enough to not really forget.
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