Heat-curable powder coating composition comprising: i) at least one crystalline polyester resin present in an amount of at least 7.5 wt%; and ii) at least one amorphous polyester resin present in an amount of at most 92.5 wt%; and iii) at least one peroxide present in an amount of at least 0.65 parts of peroxide in hundred parts of i)+ ii) (pph), wherein, - the at least one crystalline polyester resin has 2-butenedioic acid ethylenic unsaturations and/or the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations; - if the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations, then the theoretical weight per ethylenic unsaturation of the at least one amorphous polyester resin is at most 850 g/mol; - the wt% is based on the total amount of i)+ ii); - the peroxide is chosen from the group of peresters and monopercarbonates according to formula wherein R 1 represents an optionally substituted C 1-20 alkyl, a C 6-20 aryl or for OR 5, wherein R 5 represents an optionally substituted C 1-20 alkyl or for an optionally substituted C 6-20 aryl; R 2 represents an optionally substituted C 1-20 alkyl or for an optionally substituted C 6-20 aryl; and peranhydrides of formula wherein R 3 and R 4 each independently stand for an optionally, substituted C 1-20 alkyl, a C 6-20 aryl or for OR 6, wherein R 6 represents an optionally substituted C 1-10 alkyl or aC 6-20 aryl; and any combination of peroxides according to formula and formula thereof. i) at least one crystalline polyester resin present in an amount of at least 7.5 wt%; and ii) at least one amorphous polyester resin present in an amount of at most 92.5 wt%; and iii) at least one peroxide present in an amount of at least 0.65 parts of peroxide in hundred parts of i)+ ii) (pph), wherein, - the at least one crystalline polyester resin has 2-butenedioic acid ethylenic unsaturations and/or the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations; - if the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations, then the theoretical weight per ethylenic unsaturation of the at least one amorphous polyester resin is at most 850 g/mol; - the wt% is based on the total amount of i)+ ii); - the peroxide is chosen from the group of peresters and monopercarbonates according to formula wherein R 1 represents an optionally substituted C 1-20 alkyl, a C 6-20 aryl or for OR 5, wherein R 5 represents an optionally substituted C 1-20 alkyl or for an optionally substituted C 6-20 aryl; R 2 represents an optionally substituted C 1-20 alkyl or for an optionally substituted C 6-20 aryl; and peranhydrides of formula wherein R 3 and R 4 each independently stand for an optionally, substituted C 1-20 alkyl, a C 6-20 aryl or for OR 6, wherein R 6 represents an optionally substituted C 1-10 alkyl or aC 6-20 aryl; and any combination of peroxides according to formula and formula thereof. - the at least one crystalline polyester resin has 2-butenedioic acid ethylenic unsaturations and/or the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations; - if the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations, then the theoretical weight per ethylenic unsaturation of the at least one amorphous polyester resin is at most 850 g/mol; - the wt% is based on the total amount of i)+ ii); - the peroxide is chosen from the group of peresters and monopercarbonates according to formula