diff --git a/client/emv/emv_roca.c b/client/emv/emv_roca.c
index 53fd91c15..ad39d1043 100644
--- a/client/emv/emv_roca.c
+++ b/client/emv/emv_roca.c
@@ -73,6 +73,15 @@ mbedtls_mpi_uint mpi_get_uint(const mbedtls_mpi *X) {
 	return 0;
 }
 
+void print_mpi(const char *msg, int radix, const mbedtls_mpi *X) {
+	
+	char Xchar[400] = {0};
+	size_t len = 0;
+	
+	mbedtls_mpi_write_string(X, radix, Xchar, sizeof(Xchar), &len);	
+	printf("%s[%d] %s\n", msg, len, Xchar);	
+}
+
 bool emv_rocacheck(const unsigned char *buf, size_t buflen) {
 
 	mbedtls_mpi t_modulus;
@@ -83,6 +92,7 @@ bool emv_rocacheck(const unsigned char *buf, size_t buflen) {
 	rocacheck_init();
 
 	MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary(&t_modulus, buf, buflen) );
+	print_mpi("--t_modulus:", 16, &t_modulus);
 	
 	
 	for (int i = 0; i < ROCA_PRINTS_LENGTH; i++) {