diff --git a/client/emv/crypto_polarssl.c b/client/emv/crypto_polarssl.c
index 8ed38fb05..b0cb59baa 100644
--- a/client/emv/crypto_polarssl.c
+++ b/client/emv/crypto_polarssl.c
@@ -136,9 +136,15 @@ static struct crypto_pk *crypto_pk_polarssl_open_priv_rsa(va_list vl) {
     mbedtls_mpi_read_binary(&cp->ctx.Q, (const unsigned char *)q, qlen);
     mbedtls_mpi_read_binary(&cp->ctx.DP, (const unsigned char *)dp, dplen);
     mbedtls_mpi_read_binary(&cp->ctx.DQ, (const unsigned char *)dq, dqlen);
-    mbedtls_mpi_inv_mod(&cp->ctx.QP, &cp->ctx.Q, &cp->ctx.P);
+    
+    int res = mbedtls_mpi_inv_mod(&cp->ctx.QP, &cp->ctx.Q, &cp->ctx.P);
+    if (res != 0) {
+        fprintf(stderr, "PolarSSL private key error res=%x exp=%d mod=%d.\n", res * -1, explen, modlen);
+        free(cp);
+        return NULL;
+    }
 
-    int res = mbedtls_rsa_check_privkey(&cp->ctx);
+    res = mbedtls_rsa_check_privkey(&cp->ctx);
     if (res != 0) {
         fprintf(stderr, "PolarSSL private key error res=%x exp=%d mod=%d.\n", res * -1, explen, modlen);
         free(cp);