diff --git a/client/fpga_compress.c b/client/fpga_compress.c
index ee9003581..ce0f41982 100644
--- a/client/fpga_compress.c
+++ b/client/fpga_compress.c
@@ -101,7 +101,7 @@ int zlib_compress(FILE *infile[], uint8_t num_infiles, FILE *outfile, bool hardn
 			if (hardnested_mode) {
 				fprintf(stderr, "Input file too big (> %llu bytes). This is probably not a hardnested bitflip state table.\n", HARDNESTED_TABLE_SIZE);
 			} else {
-				fprintf(stderr, "Input files too big (total > %llu bytes). These are probably not PM3 FPGA config files.\n", num_infiles * FPGA_CONFIG_SIZE);
+				fprintf(stderr, "Input files too big (total > %lu bytes). These are probably not PM3 FPGA config files.\n", num_infiles * FPGA_CONFIG_SIZE);
 			}
 			for(uint16_t j = 0; j < num_infiles; j++) {
 				fclose(infile[j]);