diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c
index f0d5752dd9..4b4bcff2f4 100644
--- a/src/core/or/connection_edge.c
+++ b/src/core/or/connection_edge.c
@@ -1553,6 +1553,102 @@ consider_plaintext_ports(entry_connection_t *conn, uint16_t port)
   return 0;
 }
 
+/** Parse the given hostname in address. Returns true if the parsing was
+ * successful and type_out contains the type of the hostname. Else, false is
+ * returned which means it was not recognized and type_out is set to
+ * BAD_HOSTNAME.
+ *
+ * The possible recognized forms are (where true is returned):
+ *
+ *  If address is of the form "y.onion" with a well-formed handle y:
+ *     Put a NUL after y, lower-case it, and return ONION_V2_HOSTNAME or
+ *     ONION_V3_HOSTNAME depending on the HS version.
+ *
+ *  If address is of the form "x.y.onion" with a well-formed handle x:
+ *     Drop "x.", put a NUL after y, lower-case it, and return
+ *     ONION_V2_HOSTNAME or ONION_V3_HOSTNAME depending on the HS version.
+ *
+ * If address is of the form "y.onion" with a badly-formed handle y:
+ *     Return BAD_HOSTNAME and log a message.
+ *
+ * If address is of the form "y.exit":
+ *     Put a NUL after y and return EXIT_HOSTNAME.
+ *
+ * Otherwise:
+ *     Return NORMAL_HOSTNAME and change nothing.
+ */
+STATIC bool
+parse_extended_hostname(char *address, hostname_type_t *type_out)
+{
+  char *s;
+  char *q;
+  char query[HS_SERVICE_ADDR_LEN_BASE32+1];
+
+  s = strrchr(address,'.');
+  if (!s) {
+    *type_out = NORMAL_HOSTNAME; /* no dot, thus normal */
+    goto success;
+  }
+  if (!strcmp(s+1,"exit")) {
+    *s = 0; /* NUL-terminate it */
+    *type_out = EXIT_HOSTNAME; /* .exit */
+    goto success;
+  }
+  if (strcmp(s+1,"onion")) {
+    *type_out = NORMAL_HOSTNAME; /* neither .exit nor .onion, thus normal */
+    goto success;
+  }
+
+  /* so it is .onion */
+  *s = 0; /* NUL-terminate it */
+  /* locate a 'sub-domain' component, in order to remove it */
+  q = strrchr(address, '.');
+  if (q == address) {
+    *type_out = BAD_HOSTNAME;
+    goto failed; /* reject sub-domain, as DNS does */
+  }
+  q = (NULL == q) ? address : q + 1;
+  if (strlcpy(query, q, HS_SERVICE_ADDR_LEN_BASE32+1) >=
+      HS_SERVICE_ADDR_LEN_BASE32+1) {
+    *type_out = BAD_HOSTNAME;
+    goto failed;
+  }
+  if (q != address) {
+    memmove(address, q, strlen(q) + 1 /* also get \0 */);
+  }
+  /* v2 onion address check. */
+  if (strlen(query) == REND_SERVICE_ID_LEN_BASE32) {
+    *type_out = ONION_V2_HOSTNAME;
+    if (rend_valid_v2_service_id(query)) {
+      goto success;
+    }
+    goto failed;
+  }
+
+  /* v3 onion address check. */
+  if (strlen(query) == HS_SERVICE_ADDR_LEN_BASE32) {
+    *type_out = ONION_V3_HOSTNAME;
+    if (hs_address_is_valid(query)) {
+      goto success;
+    }
+    goto failed;
+  }
+
+  /* Reaching this point, nothing was recognized. */
+  *type_out = BAD_HOSTNAME;
+  goto failed;
+
+ success:
+  return true;
+ failed:
+  /* otherwise, return to previous state and return 0 */
+  *s = '.';
+  log_warn(LD_APP, "Invalid %shostname %s; rejecting",
+      (*type_out == (ONION_V2_HOSTNAME || ONION_V3_HOSTNAME) ? "onion " : ""),
+      safe_str_client(address));
+  return false;
+}
+
 /** How many times do we try connecting with an exit configured via
  * TrackHostExits before concluding that it won't work any more and trying a
  * different one? */
@@ -2020,16 +2116,15 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn,
   const int automap = rr.automap;
   const addressmap_entry_source_t exit_source = rr.exit_source;
 
-  /* Now, we parse the address to see if it's an .onion or .exit or
-   * other special address.
-   */
-  const hostname_type_t addresstype = parse_extended_hostname(socks->address);
-
   /* Now see whether the hostname is bogus.  This could happen because of an
    * onion hostname whose format we don't recognize. */
-  if (addresstype == BAD_HOSTNAME) {
+  hostname_type_t addresstype;
+  if (!parse_extended_hostname(socks->address, &addresstype)) {
     control_event_client_status(LOG_WARN, "SOCKS_BAD_HOSTNAME HOSTNAME=%s",
                                 escaped(socks->address));
+    if (addresstype == ONION_V3_HOSTNAME) {
+      conn->socks_request->socks_extended_error_code = SOCKS5_HS_IS_INVALID;
+    }
     connection_mark_unattached_ap(conn, END_STREAM_REASON_TORPROTOCOL);
     return -1;
   }
@@ -4312,68 +4407,6 @@ connection_ap_can_use_exit(const entry_connection_t *conn,
   return 1;
 }
 
-/** If address is of the form "y.onion" with a well-formed handle y:
- *     Put a NUL after y, lower-case it, and return ONION_V2_HOSTNAME or
- *     ONION_V3_HOSTNAME depending on the HS version.
- *
- *  If address is of the form "x.y.onion" with a well-formed handle x:
- *     Drop "x.", put a NUL after y, lower-case it, and return
- *     ONION_V2_HOSTNAME or ONION_V3_HOSTNAME depending on the HS version.
- *
- * If address is of the form "y.onion" with a badly-formed handle y:
- *     Return BAD_HOSTNAME and log a message.
- *
- * If address is of the form "y.exit":
- *     Put a NUL after y and return EXIT_HOSTNAME.
- *
- * Otherwise:
- *     Return NORMAL_HOSTNAME and change nothing.
- */
-hostname_type_t
-parse_extended_hostname(char *address)
-{
-    char *s;
-    char *q;
-    char query[HS_SERVICE_ADDR_LEN_BASE32+1];
-
-    s = strrchr(address,'.');
-    if (!s)
-      return NORMAL_HOSTNAME; /* no dot, thus normal */
-    if (!strcmp(s+1,"exit")) {
-      *s = 0; /* NUL-terminate it */
-      return EXIT_HOSTNAME; /* .exit */
-    }
-    if (strcmp(s+1,"onion"))
-      return NORMAL_HOSTNAME; /* neither .exit nor .onion, thus normal */
-
-    /* so it is .onion */
-    *s = 0; /* NUL-terminate it */
-    /* locate a 'sub-domain' component, in order to remove it */
-    q = strrchr(address, '.');
-    if (q == address) {
-      goto failed; /* reject sub-domain, as DNS does */
-    }
-    q = (NULL == q) ? address : q + 1;
-    if (strlcpy(query, q, HS_SERVICE_ADDR_LEN_BASE32+1) >=
-        HS_SERVICE_ADDR_LEN_BASE32+1)
-      goto failed;
-    if (q != address) {
-      memmove(address, q, strlen(q) + 1 /* also get \0 */);
-    }
-    if (rend_valid_v2_service_id(query)) {
-      return ONION_V2_HOSTNAME; /* success */
-    }
-    if (hs_address_is_valid(query)) {
-      return ONION_V3_HOSTNAME;
-    }
- failed:
-    /* otherwise, return to previous state and return 0 */
-    *s = '.';
-    log_warn(LD_APP, "Invalid onion hostname %s; rejecting",
-             safe_str_client(address));
-    return BAD_HOSTNAME;
-}
-
 /** Return true iff the (possibly NULL) <b>alen</b>-byte chunk of memory at
  * <b>a</b> is equal to the (possibly NULL) <b>blen</b>-byte chunk of memory
  * at <b>b</b>. */
diff --git a/src/core/or/connection_edge.h b/src/core/or/connection_edge.h
index e82b6bd765..cda087b163 100644
--- a/src/core/or/connection_edge.h
+++ b/src/core/or/connection_edge.h
@@ -71,6 +71,15 @@ entry_connection_t *EDGE_TO_ENTRY_CONN(edge_connection_t *);
 #define connection_mark_unattached_ap(conn, endreason)                  \
   connection_mark_unattached_ap_((conn), (endreason), __LINE__, SHORT_FILE__)
 
+/** Possible return values for parse_extended_hostname. */
+typedef enum hostname_type_t {
+  BAD_HOSTNAME,
+  EXIT_HOSTNAME,
+  NORMAL_HOSTNAME,
+  ONION_V2_HOSTNAME,
+  ONION_V3_HOSTNAME,
+} hostname_type_t;
+
 MOCK_DECL(void,connection_mark_unattached_ap_,
           (entry_connection_t *conn, int endreason,
            int line, const char *file));
@@ -155,13 +164,6 @@ int connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn,
                                                origin_circuit_t *circ,
                                                crypt_path_t *cpath);
 
-/** Possible return values for parse_extended_hostname. */
-typedef enum hostname_type_t {
-  NORMAL_HOSTNAME, ONION_V2_HOSTNAME, ONION_V3_HOSTNAME,
-  EXIT_HOSTNAME, BAD_HOSTNAME
-} hostname_type_t;
-hostname_type_t parse_extended_hostname(char *address);
-
 #if defined(HAVE_NET_IF_H) && defined(HAVE_NET_PFVAR_H)
 int get_pf_socket(void);
 #endif
@@ -219,6 +221,8 @@ void half_edge_free_(struct half_edge_t *he);
 
 #ifdef CONNECTION_EDGE_PRIVATE
 
+STATIC bool parse_extended_hostname(char *address, hostname_type_t *type_out);
+
 /** A parsed BEGIN or BEGIN_DIR cell */
 typedef struct begin_cell_t {
   /** The address the client has asked us to connect to, or NULL if this is
diff --git a/src/test/test_hs_common.c b/src/test/test_hs_common.c
index de3f7e04f7..9b15b3d1e1 100644
--- a/src/test/test_hs_common.c
+++ b/src/test/test_hs_common.c
@@ -6,6 +6,7 @@
  * \brief Test hidden service common functionalities.
  */
 
+#define CONNECTION_EDGE_PRIVATE
 #define HS_COMMON_PRIVATE
 #define HS_CLIENT_PRIVATE
 #define HS_SERVICE_PRIVATE
@@ -778,6 +779,7 @@ static void
 test_parse_extended_hostname(void *arg)
 {
   (void) arg;
+  hostname_type_t type;
 
   char address1[] = "fooaddress.onion";
   char address2[] = "aaaaaaaaaaaaaaaa.onion";
@@ -788,21 +790,42 @@ test_parse_extended_hostname(void *arg)
   char address7[] = ".abcdefghijklmnop.onion";
   char address8[] =
     "www.25njqamcweflpvkl73j4szahhihoc4xt3ktcgjnpaingr5yhkenl5sid.onion";
+  char address9[] =
+    "www.15njqamcweflpvkl73j4szahhihoc4xt3ktcgjnpaingr5yhkenl5sid.onion";
 
-  tt_assert(BAD_HOSTNAME == parse_extended_hostname(address1));
-  tt_assert(ONION_V2_HOSTNAME == parse_extended_hostname(address2));
-  tt_str_op(address2,OP_EQ, "aaaaaaaaaaaaaaaa");
-  tt_assert(EXIT_HOSTNAME == parse_extended_hostname(address3));
-  tt_assert(NORMAL_HOSTNAME == parse_extended_hostname(address4));
-  tt_assert(ONION_V2_HOSTNAME == parse_extended_hostname(address5));
-  tt_str_op(address5,OP_EQ, "abcdefghijklmnop");
-  tt_assert(ONION_V2_HOSTNAME == parse_extended_hostname(address6));
-  tt_str_op(address6,OP_EQ, "abcdefghijklmnop");
-  tt_assert(BAD_HOSTNAME == parse_extended_hostname(address7));
-  tt_assert(ONION_V3_HOSTNAME == parse_extended_hostname(address8));
+  tt_assert(!parse_extended_hostname(address1, &type));
+  tt_int_op(type, OP_EQ, BAD_HOSTNAME);
+
+  tt_assert(parse_extended_hostname(address2, &type));
+  tt_int_op(type, OP_EQ, ONION_V2_HOSTNAME);
+  tt_str_op(address2, OP_EQ, "aaaaaaaaaaaaaaaa");
+
+  tt_assert(parse_extended_hostname(address3, &type));
+  tt_int_op(type, OP_EQ, EXIT_HOSTNAME);
+
+  tt_assert(parse_extended_hostname(address4, &type));
+  tt_int_op(type, OP_EQ, NORMAL_HOSTNAME);
+
+  tt_assert(parse_extended_hostname(address5, &type));
+  tt_int_op(type, OP_EQ, ONION_V2_HOSTNAME);
+  tt_str_op(address5, OP_EQ, "abcdefghijklmnop");
+
+  tt_assert(parse_extended_hostname(address6, &type));
+  tt_int_op(type, OP_EQ, ONION_V2_HOSTNAME);
+  tt_str_op(address6, OP_EQ, "abcdefghijklmnop");
+
+  tt_assert(!parse_extended_hostname(address7, &type));
+  tt_int_op(type, OP_EQ, BAD_HOSTNAME);
+
+  tt_assert(parse_extended_hostname(address8, &type));
+  tt_int_op(type, OP_EQ, ONION_V3_HOSTNAME);
   tt_str_op(address8, OP_EQ,
             "25njqamcweflpvkl73j4szahhihoc4xt3ktcgjnpaingr5yhkenl5sid");
 
+  /* Invalid v3 address. */
+  tt_assert(!parse_extended_hostname(address9, &type));
+  tt_int_op(type, OP_EQ, ONION_V3_HOSTNAME);
+
  done: ;
 }