diff --git a/src/pk/rsa/rsa_exptmod.c b/src/pk/rsa/rsa_exptmod.c
index 5b50367..dcb036e 100644
--- a/src/pk/rsa/rsa_exptmod.c
+++ b/src/pk/rsa/rsa_exptmod.c
@@ -100,19 +100,27 @@ int rsa_exptmod(const unsigned char *in,   unsigned long inlen,
       }
       #endif /* LTC_RSA_BLINDING */
 
-      /* tmpa = tmp^dP mod p */
-      if ((err = mp_exptmod(tmp, key->dP, key->p, tmpa)) != CRYPT_OK)                               { goto error; }
+      if ((key->dP == NULL) || (mp_get_digit_count(key->dP) == 0)) {
+         /*
+          * In case CRT optimization parameters are not provided,
+          * the private key is directly used to exptmod it
+          */
+         if ((err = mp_exptmod(tmp, key->d, key->N, tmp)) != CRYPT_OK)                              { goto error; }
+      } else {
+         /* tmpa = tmp^dP mod p */
+         if ((err = mp_exptmod(tmp, key->dP, key->p, tmpa)) != CRYPT_OK)                            { goto error; }
 
-      /* tmpb = tmp^dQ mod q */
-      if ((err = mp_exptmod(tmp, key->dQ, key->q, tmpb)) != CRYPT_OK)                               { goto error; }
+         /* tmpb = tmp^dQ mod q */
+         if ((err = mp_exptmod(tmp, key->dQ, key->q, tmpb)) != CRYPT_OK)                            { goto error; }
 
-      /* tmp = (tmpa - tmpb) * qInv (mod p) */
-      if ((err = mp_sub(tmpa, tmpb, tmp)) != CRYPT_OK)                                              { goto error; }
-      if ((err = mp_mulmod(tmp, key->qP, key->p, tmp)) != CRYPT_OK)                                { goto error; }
+         /* tmp = (tmpa - tmpb) * qInv (mod p) */
+         if ((err = mp_sub(tmpa, tmpb, tmp)) != CRYPT_OK)                                           { goto error; }
+         if ((err = mp_mulmod(tmp, key->qP, key->p, tmp)) != CRYPT_OK)                              { goto error; }
 
-      /* tmp = tmpb + q * tmp */
-      if ((err = mp_mul(tmp, key->q, tmp)) != CRYPT_OK)                                             { goto error; }
-      if ((err = mp_add(tmp, tmpb, tmp)) != CRYPT_OK)                                               { goto error; }
+         /* tmp = tmpb + q * tmp */
+         if ((err = mp_mul(tmp, key->q, tmp)) != CRYPT_OK)                                          { goto error; }
+         if ((err = mp_add(tmp, tmpb, tmp)) != CRYPT_OK)                                            { goto error; }
+      }
 
       #ifdef LTC_RSA_BLINDING
       /* unblind */
diff --git a/testprof/rsa_test.c b/testprof/rsa_test.c
index ae27ec1..7e7e45c 100644
--- a/testprof/rsa_test.c
+++ b/testprof/rsa_test.c
@@ -291,6 +291,26 @@ for (cnt = 0; cnt < len; ) {
       return 1;
    }
 
+   /* verify with privKey but remove pointer to dP to test without CRT */
+
+   void* dP = privKey.dP;
+   privKey.dP = NULL;
+   /* change byte back to original */
+   in[0] ^= 1;
+   DO(rsa_verify_hash(out, len, in, 20, hash_idx, 0, &stat, &privKey));
+   /* change a byte */
+   in[0] ^= 1;
+   DO(rsa_verify_hash(out, len, in, 20, hash_idx, 0, &stat2, &privKey));
+
+   if (!(stat == 1 && stat2 == 0)) {
+      fprintf(stderr, "rsa_verify_hash (unsalted, privKey) failed, %d, %d", stat, stat2);
+      rsa_free(&key);
+      rsa_free(&pubKey);
+      rsa_free(&privKey);
+      return 1;
+   }
+   privKey.dP = dP;
+
    /* verify with pubKey */
    /* change byte back to original */
    in[0] ^= 1;