diff --git a/lib/vtls/gtls.c b/lib/vtls/gtls.c
index f4cbe88080..7c62271326 100644
--- a/lib/vtls/gtls.c
+++ b/lib/vtls/gtls.c
@@ -323,8 +323,8 @@ gnutls_set_ssl_version_min_max(struct Curl_easy *data,
   long ssl_version = conn_config->version;
   long ssl_version_max = conn_config->version_max;
 
-  if((ssl_version == CURL_SSLVERSION_DEFAULT) ||
-     (ssl_version == CURL_SSLVERSION_TLSv1))
+  DEBUGASSERT(ssl_version != CURL_SSLVERSION_DEFAULT);
+  if(ssl_version <= CURL_SSLVERSION_TLSv1)
     ssl_version = CURL_SSLVERSION_TLSv1_0;
   if((ssl_version_max == CURL_SSLVERSION_MAX_NONE) ||
      (ssl_version_max == CURL_SSLVERSION_MAX_DEFAULT))
diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
index b4ef84799d..8e4912a45f 100644
--- a/lib/vtls/mbedtls.c
+++ b/lib/vtls/mbedtls.c
@@ -198,8 +198,8 @@ mbed_set_ssl_version_min_max(struct Curl_easy *data,
 #endif
     ;
 
+  DEBUGASSERT(conn_config->version != CURL_SSLVERSION_DEFAULT);
   switch(conn_config->version) {
-  case CURL_SSLVERSION_DEFAULT:
   case CURL_SSLVERSION_TLSv1:
   case CURL_SSLVERSION_TLSv1_0:
   case CURL_SSLVERSION_TLSv1_1:
diff --git a/lib/vtls/openssl.c b/lib/vtls/openssl.c
index ae1fe6cbb1..d6996d680f 100644
--- a/lib/vtls/openssl.c
+++ b/lib/vtls/openssl.c
@@ -3620,11 +3620,11 @@ static CURLcode ossl_init_method(struct Curl_cfilter *cf,
 
   *pmethod = NULL;
   *pssl_version_min = conn_config->version;
+  DEBUGASSERT(conn_config->version != CURL_SSLVERSION_DEFAULT);
   switch(peer->transport) {
   case TRNSPRT_TCP:
     /* check to see if we have been told to use an explicit SSL/TLS version */
     switch(*pssl_version_min) {
-    case CURL_SSLVERSION_DEFAULT:
     case CURL_SSLVERSION_TLSv1:
     case CURL_SSLVERSION_TLSv1_0:
     case CURL_SSLVERSION_TLSv1_1:
@@ -3770,13 +3770,13 @@ CURLcode Curl_ossl_ctx_init(struct ossl_ctx *octx,
   if(!ssl_config->enable_beast)
     ctx_options &= ~(ctx_option_t)SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
 
+  DEBUGASSERT(ssl_version_min != CURL_SSLVERSION_DEFAULT);
   switch(ssl_version_min) {
   case CURL_SSLVERSION_SSLv2:
   case CURL_SSLVERSION_SSLv3:
     return CURLE_NOT_BUILT_IN;
 
     /* "--tlsv<x.y>" options mean TLS >= version <x.y> */
-  case CURL_SSLVERSION_DEFAULT:
   case CURL_SSLVERSION_TLSv1:   /* TLS >= version 1.0 */
   case CURL_SSLVERSION_TLSv1_0: /* TLS >= version 1.0 */
   case CURL_SSLVERSION_TLSv1_1: /* TLS >= version 1.1 */
diff --git a/lib/vtls/rustls.c b/lib/vtls/rustls.c
index 79c8146b0d..a326aae877 100644
--- a/lib/vtls/rustls.c
+++ b/lib/vtls/rustls.c
@@ -533,8 +533,8 @@ init_config_builder(struct Curl_easy *data,
   CURLcode result = CURLE_OK;
   rustls_result rr;
 
+  DEBUGASSERT(conn_config->version != CURL_SSLVERSION_DEFAULT);
   switch(conn_config->version) {
-  case CURL_SSLVERSION_DEFAULT:
   case CURL_SSLVERSION_TLSv1:
   case CURL_SSLVERSION_TLSv1_0:
   case CURL_SSLVERSION_TLSv1_1:
diff --git a/lib/vtls/schannel.c b/lib/vtls/schannel.c
index fd268c92a3..d90c86d99f 100644
--- a/lib/vtls/schannel.c
+++ b/lib/vtls/schannel.c
@@ -428,8 +428,8 @@ static CURLcode schannel_acquire_credential_handle(struct Curl_cfilter *cf,
   else
     infof(data, "schannel: enabled automatic use of client certificate");
 
+  DEBUGASSERT(conn_config->version != CURL_SSLVERSION_DEFAULT);
   switch(conn_config->version) {
-  case CURL_SSLVERSION_DEFAULT:
   case CURL_SSLVERSION_TLSv1:
   case CURL_SSLVERSION_TLSv1_0:
   case CURL_SSLVERSION_TLSv1_1:
diff --git a/lib/vtls/wolfssl.c b/lib/vtls/wolfssl.c
index 84180cad4e..a90b5bf439 100644
--- a/lib/vtls/wolfssl.c
+++ b/lib/vtls/wolfssl.c
@@ -1028,8 +1028,9 @@ static CURLcode ssl_version(struct Curl_easy *data,
 {
   int res;
   *min_version = *max_version = 0;
+  DEBUGASSERT(conn_config->version != CURL_SSLVERSION_DEFAULT);
+
   switch(conn_config->version) {
-  case CURL_SSLVERSION_DEFAULT:
   case CURL_SSLVERSION_TLSv1:
   case CURL_SSLVERSION_TLSv1_0:
     *min_version = TLS1_VERSION;