diff --git a/tests/pkcs_1_eme_test.c b/tests/pkcs_1_eme_test.c
index e709156..425c883 100644
--- a/tests/pkcs_1_eme_test.c
+++ b/tests/pkcs_1_eme_test.c
@@ -48,7 +48,9 @@ int pkcs_1_eme_test(void)
     mp_clear_multi(key->d,  key->e, key->N, key->dQ, key->dP, key->qP, key->p, key->q, NULL);
   } /* for */
 
+#ifndef LTC_PTHREAD
   unregister_prng(&no_prng_desc);
+#endif
 
   return 0;
 }
diff --git a/tests/pkcs_1_oaep_test.c b/tests/pkcs_1_oaep_test.c
index ae1aee3..8be42d3 100644
--- a/tests/pkcs_1_oaep_test.c
+++ b/tests/pkcs_1_oaep_test.c
@@ -48,7 +48,9 @@ int pkcs_1_oaep_test(void)
     mp_clear_multi(key->d,  key->e, key->N, key->dQ, key->dP, key->qP, key->p, key->q, NULL);
   } /* for */
 
+#ifndef LTC_PTHREAD
   unregister_prng(&no_prng_desc);
+#endif
 
   return 0;
 }
diff --git a/tests/pkcs_1_pss_test.c b/tests/pkcs_1_pss_test.c
index 76822c9..c7b352b 100644
--- a/tests/pkcs_1_pss_test.c
+++ b/tests/pkcs_1_pss_test.c
@@ -49,7 +49,9 @@ int pkcs_1_pss_test(void)
     mp_clear_multi(key->d,  key->e, key->N, key->dQ, key->dP, key->qP, key->p, key->q, NULL);
   } /* for */
 
+#ifndef LTC_PTHREAD
   unregister_prng(&no_prng_desc);
+#endif
 
   return 0;
 }