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We study the impact of stellar cooling due to light axion emission on the formation and evolution of black hole binaries, via stable mass transfer and the common envelope scenario.~We find that in the presence of light axion emission, no binary black hole mergers are formed with black holes in the lower mass gap ($$M_{\rm BH} < 4 {\rm M}_\odot $$) via the common envelope formation channel.~In some systems, this happens because axions prevent Roche lobe overflow.~In others, they prevent the common envelope from being ejected.~Our results apply to axions with couplings $$ g_{a \gamma} \gtrsim 10^{-10}\, \rm GeV^{-1}$$ (to photons) or $$\alpha_{ae} \gtrsim 10^{-26} $$ (to electrons) and masses $$ m_a \ll 10 \, \rm keV$$.~Light, weakly coupled particles may therefore apparently produce a mass gap $$2 {\rm M}_\odot < M_{\rm BH} < 4 {\rm M}_\odot$$ in the LIGO/Virgo/KAGRA data, when no mass gap is present in the stellar remnant population.