diff --git a/configure.ac b/configure.ac
index 4aba828b3..1958e62ca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7004,7 +7004,7 @@ AC_ARG_WITH([cavium-v],
         ENABLED_CAVIUM_V=yes
     ],
     [
-        ENABLED_CAVIUM_=no
+        ENABLED_CAVIUM=no
         ENABLED_CAVIUM_V=no
     ]
 )
@@ -7804,6 +7804,30 @@ then
     AC_MSG_ERROR([please use --with-libz if enabling mcapi.])
 fi
 
+
+# cryptodev is old name, replaced with cryptocb
+AC_ARG_ENABLE([cryptodev],
+    [AS_HELP_STRING([--enable-cryptodev],[DEPRECATED, use cryptocb instead])],
+    [ ENABLED_CRYPTOCB=$enableval ],[ ENABLED_CRYPTOCB=no ])
+
+# Support for crypto callbacks
+AC_ARG_ENABLE([cryptocb],
+    [AS_HELP_STRING([--enable-cryptocb],[Enable crypto callbacks (default: disabled)])],
+    [ ENABLED_CRYPTOCB=$enableval ],
+    [ ENABLED_CRYPTOCB=no ]
+    )
+
+if test "x$ENABLED_PKCS11" = "xyes" || test "x$ENABLED_WOLFTPM" = "xyes" || test "$ENABLED_CAAM" != "no"
+then
+    ENABLED_CRYPTOCB=yes
+fi
+if test "$ENABLED_CRYPTOCB" = "yes"
+then
+    AM_CFLAGS="$AM_CFLAGS -DWOLF_CRYPTO_CB"
+fi
+
+
+
 # Asynchronous Crypto
 AC_ARG_ENABLE([asynccrypt],
     [AS_HELP_STRING([--enable-asynccrypt],[Enable Asynchronous Crypto (default: disabled)])],
@@ -7826,6 +7850,7 @@ fi
 
 if test "$ENABLED_ASYNCCRYPT" = "yes"
 then
+    AC_MSG_NOTICE([Enabling asynchronous support])
     if ! test -f ${srcdir}/wolfcrypt/src/async.c || ! test -f ${srcdir}/wolfssl/wolfcrypt/async.h
     then
         AC_MSG_ERROR([--enable-asynccrypt requested, but WOLFSSL_ASYNC_CRYPT source files are missing.])
@@ -7835,15 +7860,14 @@ then
 
     # If no async backend (hardware or software) has been explicitly enabled,
     # use the software backend for testing.
-    if test "x$ENABLED_CAVIUM" = "xno" && test "x$ENABLED_INTEL_QA" = "xno" &&
-       test "x$ENABLED_ASYNCCRYPT_SW" = "xno"
+    if test "x$ENABLED_CAVIUM" != "xyes" && test "x$ENABLED_INTEL_QA" != "xyes" && test "x$ENABLED_CRYPTOCB" != "xyes" && test "x$ENABLED_PKCALLBACKS" != "xyes" && test "x$ENABLED_ASYNCCRYPT_SW" != "xyes"
     then
-        # Async threading is Linux specific
+        AC_MSG_NOTICE([Enabling asynchronous software simulator])
         AM_CFLAGS="$AM_CFLAGS -DWOLFSSL_ASYNC_CRYPT_SW"
+        ENABLED_ASYNCCRYPT_SW=yes
     fi
 fi
 
-
 # check for async if using Intel QuckAssist or Cavium
 if test "x$ENABLED_INTEL_QA" = "xyes" || test "x$ENABLED_CAVIUM" = "xyes" ; then
     if test "x$ENABLED_ASYNCCRYPT" = "xno" ; then
@@ -7851,8 +7875,7 @@ if test "x$ENABLED_INTEL_QA" = "xyes" || test "x$ENABLED_CAVIUM" = "xyes" ; then
     fi
 fi
 
-
-# Asynchronous threading
+# Asynchronous threading (Linux specific)
 AC_ARG_ENABLE([asyncthreads],
     [AS_HELP_STRING([--enable-asyncthreads],[Enable Asynchronous Threading (default: enabled)])],
     [ ENABLED_ASYNCTHREADS=$enableval ],
@@ -7875,28 +7898,6 @@ else
 fi
 
 
-# cryptodev is old name, replaced with cryptocb
-AC_ARG_ENABLE([cryptodev],
-    [AS_HELP_STRING([--enable-cryptodev],[DEPRECATED, use cryptocb instead])],
-    [ ENABLED_CRYPTOCB=$enableval ],[ ENABLED_CRYPTOCB=no ])
-
-# Support for crypto callbacks
-AC_ARG_ENABLE([cryptocb],
-    [AS_HELP_STRING([--enable-cryptocb],[Enable crypto callbacks (default: disabled)])],
-    [ ENABLED_CRYPTOCB=$enableval ],
-    [ ENABLED_CRYPTOCB=no ]
-    )
-
-if test "x$ENABLED_PKCS11" = "xyes" || test "x$ENABLED_WOLFTPM" = "xyes" || test "$ENABLED_CAAM" != "no"
-then
-    ENABLED_CRYPTOCB=yes
-fi
-if test "$ENABLED_CRYPTOCB" = "yes"
-then
-    AM_CFLAGS="$AM_CFLAGS -DWOLF_CRYPTO_CB"
-fi
-
-
 # Session Export
 AC_ARG_ENABLE([sessionexport],
     [AS_HELP_STRING([--enable-sessionexport],[Enable export and import of sessions (default: disabled)])],
@@ -9515,7 +9516,8 @@ echo "   * Stack sizes in tests:       $ENABLED_STACKSIZE"
 echo "   * Heap stats in tests:        $ENABLED_TRACKMEMORY"
 echo "   * User Crypto:                $ENABLED_USER_CRYPTO"
 echo "   * Fast RSA:                   $ENABLED_FAST_RSA"
-echo "   * Async Crypto:               $ENABLED_ASYNCCRYPT"
+echo "   * Asynchronous Crypto:        $ENABLED_ASYNCCRYPT"
+echo "   * Asynchronous Crypto (sim):  $ENABLED_ASYNCCRYPT_SW"
 echo "   * PKCS#8:                     $ENABLED_PKCS8"
 echo "   * PKCS#11:                    $ENABLED_PKCS11"
 echo "   * PKCS#12:                    $ENABLED_PKCS12"
@@ -9536,6 +9538,7 @@ echo "   * Inline Code:                $ENABLED_INLINE"
 echo "   * Linux AF_ALG:               $ENABLED_AFALG"
 echo "   * Linux KCAPI:                $ENABLED_KCAPI"
 echo "   * Linux devcrypto:            $ENABLED_DEVCRYPTO"
+echo "   * PK callbacks:               $ENABLED_PKCALLBACKS"
 echo "   * Crypto callbacks:           $ENABLED_CRYPTOCB"
 echo "   * i.MX CAAM:                  $ENABLED_CAAM"
 echo "   * IoT-Safe:                   $ENABLED_IOTSAFE"
diff --git a/wolfcrypt/src/aes.c b/wolfcrypt/src/aes.c
index fd2f9e0e5..d57c124cd 100644
--- a/wolfcrypt/src/aes.c
+++ b/wolfcrypt/src/aes.c
@@ -4152,7 +4152,7 @@ int wc_AesCbcEncrypt(Aes* aes, byte* out, const byte* in, word32 sz)
             return IntelQaSymAesCbcEncrypt(&aes->asyncDev, out, in, sz,
                 (const byte*)aes->devKey, aes->keylen,
                 (byte*)aes->reg, AES_BLOCK_SIZE);
-        #else /* WOLFSSL_ASYNC_CRYPT_SW */
+        #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
             if (wc_AsyncSwInit(&aes->asyncDev, ASYNC_SW_AES_CBC_ENCRYPT)) {
                 WC_ASYNC_SW* sw = &aes->asyncDev.sw;
                 sw->aes.aes = aes;
@@ -4317,7 +4317,7 @@ int wc_AesCbcEncrypt(Aes* aes, byte* out, const byte* in, word32 sz)
             return IntelQaSymAesCbcDecrypt(&aes->asyncDev, out, in, sz,
                 (const byte*)aes->devKey, aes->keylen,
                 (byte*)aes->reg, AES_BLOCK_SIZE);
-        #else /* WOLFSSL_ASYNC_CRYPT_SW */
+        #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
             if (wc_AsyncSwInit(&aes->asyncDev, ASYNC_SW_AES_CBC_DECRYPT)) {
                 WC_ASYNC_SW* sw = &aes->asyncDev.sw;
                 sw->aes.aes = aes;
@@ -6887,7 +6887,7 @@ int wc_AesGcmEncrypt(Aes* aes, byte* out, const byte* in, word32 sz,
         return IntelQaSymAesGcmEncrypt(&aes->asyncDev, out, in, sz,
             (const byte*)aes->devKey, aes->keylen, iv, ivSz,
             authTag, authTagSz, authIn, authInSz);
-    #else /* WOLFSSL_ASYNC_CRYPT_SW */
+    #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
         if (wc_AsyncSwInit(&aes->asyncDev, ASYNC_SW_AES_GCM_ENCRYPT)) {
             WC_ASYNC_SW* sw = &aes->asyncDev.sw;
             sw->aes.aes = aes;
@@ -7447,7 +7447,7 @@ int wc_AesGcmDecrypt(Aes* aes, byte* out, const byte* in, word32 sz,
         return IntelQaSymAesGcmDecrypt(&aes->asyncDev, out, in, sz,
             (const byte*)aes->devKey, aes->keylen, iv, ivSz,
             authTag, authTagSz, authIn, authInSz);
-    #else /* WOLFSSL_ASYNC_CRYPT_SW */
+    #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
         if (wc_AsyncSwInit(&aes->asyncDev, ASYNC_SW_AES_GCM_DECRYPT)) {
             WC_ASYNC_SW* sw = &aes->asyncDev.sw;
             sw->aes.aes = aes;
diff --git a/wolfcrypt/src/des3.c b/wolfcrypt/src/des3.c
index 741cfce65..650c33a36 100644
--- a/wolfcrypt/src/des3.c
+++ b/wolfcrypt/src/des3.c
@@ -1616,7 +1616,7 @@
         #elif defined(HAVE_INTEL_QA)
             return IntelQaSymDes3CbcEncrypt(&des->asyncDev, out, in, sz,
                 (const byte*)des->devKey, DES3_KEYLEN, (byte*)des->reg, DES3_IVLEN);
-        #else /* WOLFSSL_ASYNC_CRYPT_SW */
+        #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
             if (wc_AsyncSwInit(&des->asyncDev, ASYNC_SW_DES3_CBC_ENCRYPT)) {
                 WC_ASYNC_SW* sw = &des->asyncDev.sw;
                 sw->des.des = des;
@@ -1667,7 +1667,7 @@
         #elif defined(HAVE_INTEL_QA)
             return IntelQaSymDes3CbcDecrypt(&des->asyncDev, out, in, sz,
                 (const byte*)des->devKey, DES3_KEYLEN, (byte*)des->reg, DES3_IVLEN);
-        #else /* WOLFSSL_ASYNC_CRYPT_SW */
+        #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
             if (wc_AsyncSwInit(&des->asyncDev, ASYNC_SW_DES3_CBC_DECRYPT)) {
                 WC_ASYNC_SW* sw = &des->asyncDev.sw;
                 sw->des.des = des;
diff --git a/wolfcrypt/src/dh.c b/wolfcrypt/src/dh.c
index 086fc048d..e638a51ce 100644
--- a/wolfcrypt/src/dh.c
+++ b/wolfcrypt/src/dh.c
@@ -1433,7 +1433,7 @@ static int wc_DhGenerateKeyPair_Async(DhKey* key, WC_RNG* rng,
 #elif defined(HAVE_CAVIUM)
     /* TODO: Not implemented - use software for now */
 
-#else /* WOLFSSL_ASYNC_CRYPT_SW */
+#elif defined(WOLFSSL_ASYNC_CRYPT_SW)
     if (wc_AsyncSwInit(&key->asyncDev, ASYNC_SW_DH_GEN)) {
         WC_ASYNC_SW* sw = &key->asyncDev.sw;
         sw->dhGen.key = key;
@@ -2207,7 +2207,7 @@ static int wc_DhAgree_Async(DhKey* key, byte* agree, word32* agreeSz,
 #elif defined(HAVE_CAVIUM)
     /* TODO: Not implemented - use software for now */
 
-#else /* WOLFSSL_ASYNC_CRYPT_SW */
+#elif defined(WOLFSSL_ASYNC_CRYPT_SW)
     if (wc_AsyncSwInit(&key->asyncDev, ASYNC_SW_DH_AGREE)) {
         WC_ASYNC_SW* sw = &key->asyncDev.sw;
         sw->dhAgree.key = key;
diff --git a/wolfcrypt/src/ecc.c b/wolfcrypt/src/ecc.c
index eaff8ae8c..59ff57aa6 100644
--- a/wolfcrypt/src/ecc.c
+++ b/wolfcrypt/src/ecc.c
@@ -5495,7 +5495,7 @@ static int _ecc_make_key_ex(WC_RNG* rng, int keysize, ecc_key* key,
         /* TODO: Not implemented */
     #elif defined(HAVE_INTEL_QA)
         /* Implemented in ecc_make_pub_ex for the pub calc */
-    #else
+    #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
         if (wc_AsyncSwInit(&key->asyncDev, ASYNC_SW_ECC_MAKE)) {
             WC_ASYNC_SW* sw = &key->asyncDev.sw;
             sw->eccMake.rng = rng;
diff --git a/wolfcrypt/src/rsa.c b/wolfcrypt/src/rsa.c
index a1446c863..bc2ff370a 100644
--- a/wolfcrypt/src/rsa.c
+++ b/wolfcrypt/src/rsa.c
@@ -2767,7 +2767,7 @@ static int wc_RsaFunctionAsync(const byte* in, word32 inLen, byte* out,
     }
 #endif /* WOLFSSL_ASYNC_CRYPT_SW */
 
-    switch(type) {
+    switch (type) {
 #ifndef WOLFSSL_RSA_PUBLIC_ONLY
     case RSA_PRIVATE_DECRYPT:
     case RSA_PRIVATE_ENCRYPT:
@@ -2789,7 +2789,7 @@ static int wc_RsaFunctionAsync(const byte* in, word32 inLen, byte* out,
                                 &key->u.raw,
                                 out, outLen);
         #endif
-    #else /* WOLFSSL_ASYNC_CRYPT_SW */
+    #else
         ret = wc_RsaFunctionSync(in, inLen, out, outLen, type, key, rng);
     #endif
         break;
@@ -2807,7 +2807,7 @@ static int wc_RsaFunctionAsync(const byte* in, word32 inLen, byte* out,
         ret = IntelQaRsaPublic(&key->asyncDev, in, inLen,
                                &key->e.raw, &key->n.raw,
                                out, outLen);
-    #else /* WOLFSSL_ASYNC_CRYPT_SW */
+    #else
         ret = wc_RsaFunctionSync(in, inLen, out, outLen, type, key, rng);
     #endif
         break;
@@ -4734,7 +4734,7 @@ int wc_MakeRsaKey(RsaKey* key, int size, long e, WC_RNG* rng)
     #elif defined(HAVE_INTEL_QA)
         err = IntelQaRsaKeyGen(&key->asyncDev, key, size, e, rng);
         goto out;
-    #else
+    #elif defined(WOLFSSL_ASYNC_CRYPT_SW)
         if (wc_AsyncSwInit(&key->asyncDev, ASYNC_SW_RSA_MAKE)) {
             WC_ASYNC_SW* sw = &key->asyncDev.sw;
             sw->rsaMake.rng = rng;
diff --git a/wolfssl/wolfcrypt/settings.h b/wolfssl/wolfcrypt/settings.h
index 7e44d312c..0f9bb0104 100644
--- a/wolfssl/wolfcrypt/settings.h
+++ b/wolfssl/wolfcrypt/settings.h
@@ -2473,6 +2473,7 @@ extern void uITRON4_free(void *p) ;
 /* Asynchronous Crypto */
 #ifdef WOLFSSL_ASYNC_CRYPT
     #if !defined(HAVE_CAVIUM) && !defined(HAVE_INTEL_QA) && \
+        !defined(WOLF_CRYPTO_CB) && !defined(HAVE_PK_CALLBACKS) && \
         !defined(WOLFSSL_ASYNC_CRYPT_SW)
         #error No async backend defined with WOLFSSL_ASYNC_CRYPT!
     #endif