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The use of hydrogen in a spark ignited engine is accompanied by a significant risk for backfire and knock, especially at full load, where the richest mixture is used. In fact, when attempting to maximize engine power, knock can (and usually will) lead to runaway surface ignition and backfire without much delay. Since backfire (and knock) has to be avoided at all cost, an attempt was made to detect and quantify knock from the measured pressure traces. For future use knock detection, combined with multipoint timed hydrogen injection, offers the possibility to avoid backfire by temporarily cylinder deactivation. In a first attempt the standard method using the third derivative of the pressure was tried, but proved to be too insensitive to be of any practical use, even though knock was very audible and the pressure oscillations are easily visible on the measurements. This insensitivity is caused by the very fast combustion achieved with hydrogen, compared to other fuels.