British number one Kyle Edmund's first match of the clay-court season lasted only 16 minutes as Jiri Vesely retired.
World number 26 Edmund, 23, was leading 5-0 in the first set of the first-round match in the Grand Prix Hassan II in Marrakesh when Czech Vesely withdrew.
It was Edmund's first win since reaching the Australian Open semi-finals in January, having lost early on at Indian Wells and Miami.
Second seed Edmund will face Radu Albot or Andreas Seppi in the last 16.
Spain's Albert Ramos-Vinolas, the top seed, earlier beat Moroccan wildcard Amine Ahouda 6-1 6-2, while fifth seed Robin Haase and seventh seed Alexandr Dolgopolov lost.