diff --git a/challenge/dns01/client.go b/challenge/dns01/client.go
index 919ce1c2d..58a692e76 100644
--- a/challenge/dns01/client.go
+++ b/challenge/dns01/client.go
@@ -84,10 +84,10 @@ func (c *Client) sendQuery(ctx context.Context, fqdn string, rtype uint16, recur
 }
 
 func (c *Client) sendQueryCustom(ctx context.Context, fqdn string, rtype uint16, nameservers []string, recursive bool) (*dns.Msg, error) {
-	m := createDNSMsg(fqdn, rtype, recursive)
+	m := internal.CreateDNSMsg(fqdn, rtype, recursive)
 
 	if len(nameservers) == 0 {
-		return nil, &DNSError{Message: "empty list of nameservers"}
+		return nil, &internal.DNSError{Message: "empty list of nameservers"}
 	}
 
 	var (
@@ -116,7 +116,7 @@ func (c *Client) exchange(ctx context.Context, m *dns.Msg, ns string) (*dns.Msg,
 	if c.tcpOnly {
 		r, _, err := c.tcpClient.ExchangeContext(ctx, m, ns)
 		if err != nil {
-			return r, &DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
+			return r, &internal.DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
 		}
 
 		return r, nil
@@ -130,20 +130,8 @@ func (c *Client) exchange(ctx context.Context, m *dns.Msg, ns string) (*dns.Msg,
 	}
 
 	if err != nil {
-		return r, &DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
+		return r, &internal.DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
 	}
 
 	return r, nil
 }
-
-func createDNSMsg(fqdn string, rtype uint16, recursive bool) *dns.Msg {
-	m := new(dns.Msg)
-	m.SetQuestion(fqdn, rtype)
-	m.SetEdns0(4096, false)
-
-	if !recursive {
-		m.RecursionDesired = false
-	}
-
-	return m
-}
diff --git a/challenge/dns01/client_zone.go b/challenge/dns01/client_zone.go
index 59f7c1b6d..ac1bf6f6c 100644
--- a/challenge/dns01/client_zone.go
+++ b/challenge/dns01/client_zone.go
@@ -82,9 +82,9 @@ func (c *Client) fetchSoaByFqdn(ctx context.Context, fqdn string, nameservers []
 			// NXDOMAIN
 		default:
 			// Any response code other than NOERROR and NXDOMAIN is treated as error
-			return nil, &DNSError{Message: fmt.Sprintf("unexpected response for '%s'", domain), MsgOut: r}
+			return nil, &internal.DNSError{Message: fmt.Sprintf("unexpected response for '%s'", domain), MsgOut: r}
 		}
 	}
 
-	return nil, &DNSError{Message: fmt.Sprintf("could not find the start of authority for '%s'", fqdn), MsgOut: r, Err: err}
+	return nil, &internal.DNSError{Message: fmt.Sprintf("could not find the start of authority for '%s'", fqdn), MsgOut: r, Err: err}
 }
diff --git a/challenge/dnspersist01/client.go b/challenge/dnspersist01/client.go
index 30c2638d4..5558baf7a 100644
--- a/challenge/dnspersist01/client.go
+++ b/challenge/dnspersist01/client.go
@@ -82,10 +82,10 @@ func (c *Client) sendQuery(ctx context.Context, fqdn string, rtype uint16, recur
 }
 
 func (c *Client) sendQueryCustom(ctx context.Context, fqdn string, rtype uint16, nameservers []string, recursive bool) (*dns.Msg, error) {
-	m := createDNSMsg(fqdn, rtype, recursive)
+	m := internal.CreateDNSMsg(fqdn, rtype, recursive)
 
 	if len(nameservers) == 0 {
-		return nil, &DNSError{Message: "empty list of nameservers"}
+		return nil, &internal.DNSError{Message: "empty list of nameservers"}
 	}
 
 	var (
@@ -118,7 +118,7 @@ func (c *Client) exchange(ctx context.Context, m *dns.Msg, ns string) (*dns.Msg,
 	if c.tcpOnly {
 		r, _, err := c.tcpClient.ExchangeContext(ctx, m, ns)
 		if err != nil {
-			return r, &DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
+			return r, &internal.DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
 		}
 
 		return r, nil
@@ -132,24 +132,8 @@ func (c *Client) exchange(ctx context.Context, m *dns.Msg, ns string) (*dns.Msg,
 	}
 
 	if err != nil {
-		return r, &DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
+		return r, &internal.DNSError{Message: "DNS call error", MsgIn: m, NS: ns, Err: err}
 	}
 
 	return r, nil
 }
-
-/*
- * NOTE(ldez): This function is a duplication of `Client.createDNSMsg()` from `dns01/client.go`.
- * The 2 functions should be kept in sync.
- */
-func createDNSMsg(fqdn string, rtype uint16, recursive bool) *dns.Msg {
-	m := new(dns.Msg)
-	m.SetQuestion(fqdn, rtype)
-	m.SetEdns0(4096, false)
-
-	if !recursive {
-		m.RecursionDesired = false
-	}
-
-	return m
-}
diff --git a/challenge/dnspersist01/client_error.go b/challenge/dnspersist01/client_error.go
deleted file mode 100644
index 1ec9e58fc..000000000
--- a/challenge/dnspersist01/client_error.go
+++ /dev/null
@@ -1,69 +0,0 @@
-package dnspersist01
-
-/*
- * NOTE(ldez): This file is a duplication of `dns01/client_error.go`.
- * The 2 files should be kept in sync.
- */
-
-import (
-	"fmt"
-	"strings"
-
-	"github.com/miekg/dns"
-)
-
-// DNSError error related to DNS calls.
-type DNSError struct {
-	Message string
-	NS      string
-	MsgIn   *dns.Msg
-	MsgOut  *dns.Msg
-	Err     error
-}
-
-func (d *DNSError) Error() string {
-	var details []string
-	if d.NS != "" {
-		details = append(details, "ns="+d.NS)
-	}
-
-	if d.MsgIn != nil && len(d.MsgIn.Question) > 0 {
-		details = append(details, fmt.Sprintf("question='%s'", formatQuestions(d.MsgIn.Question)))
-	}
-
-	if d.MsgOut != nil {
-		if d.MsgIn == nil || len(d.MsgIn.Question) == 0 {
-			details = append(details, fmt.Sprintf("question='%s'", formatQuestions(d.MsgOut.Question)))
-		}
-
-		details = append(details, "code="+dns.RcodeToString[d.MsgOut.Rcode])
-	}
-
-	msg := "DNS error"
-	if d.Message != "" {
-		msg = d.Message
-	}
-
-	if d.Err != nil {
-		msg += ": " + d.Err.Error()
-	}
-
-	if len(details) > 0 {
-		msg += " [" + strings.Join(details, ", ") + "]"
-	}
-
-	return msg
-}
-
-func (d *DNSError) Unwrap() error {
-	return d.Err
-}
-
-func formatQuestions(questions []dns.Question) string {
-	var parts []string
-	for _, question := range questions {
-		parts = append(parts, strings.ReplaceAll(strings.TrimPrefix(question.String(), ";"), "\t", " "))
-	}
-
-	return strings.Join(parts, ";")
-}
diff --git a/challenge/dnspersist01/client_txt.go b/challenge/dnspersist01/client_txt.go
index 2f514283b..3755ddcfa 100644
--- a/challenge/dnspersist01/client_txt.go
+++ b/challenge/dnspersist01/client_txt.go
@@ -90,7 +90,7 @@ func (c *Client) lookupTXT(ctx context.Context, fqdn string, nameservers []strin
 		case dns.RcodeNameError:
 			return result, nil
 		default:
-			return result, &DNSError{Message: fmt.Sprintf("unexpected response for '%s'", name), MsgOut: msg}
+			return result, &internal.DNSError{Message: fmt.Sprintf("unexpected response for '%s'", name), MsgOut: msg}
 		}
 	}
 }
diff --git a/challenge/dnspersist01/client_zone.go b/challenge/dnspersist01/client_zone.go
index 7c2c3ff8c..10fb2d66d 100644
--- a/challenge/dnspersist01/client_zone.go
+++ b/challenge/dnspersist01/client_zone.go
@@ -75,9 +75,9 @@ func (c *Client) fetchSoaByFqdn(ctx context.Context, fqdn string, nameservers []
 			// NXDOMAIN
 		default:
 			// Any response code other than NOERROR and NXDOMAIN is treated as error
-			return "", &DNSError{Message: fmt.Sprintf("unexpected response for '%s'", domain), MsgOut: r}
+			return "", &internal.DNSError{Message: fmt.Sprintf("unexpected response for '%s'", domain), MsgOut: r}
 		}
 	}
 
-	return "", &DNSError{Message: fmt.Sprintf("could not find the start of authority for '%s'", fqdn), MsgOut: r, Err: err}
+	return "", &internal.DNSError{Message: fmt.Sprintf("could not find the start of authority for '%s'", fqdn), MsgOut: r, Err: err}
 }
diff --git a/challenge/dns01/client_error.go b/challenge/internal/client_error.go
similarity index 98%
rename from challenge/dns01/client_error.go
rename to challenge/internal/client_error.go
index 644140075..c3cf6d53e 100644
--- a/challenge/dns01/client_error.go
+++ b/challenge/internal/client_error.go
@@ -1,4 +1,4 @@
-package dns01
+package internal
 
 import (
 	"fmt"
diff --git a/challenge/dns01/client_error_test.go b/challenge/internal/client_error_test.go
similarity index 90%
rename from challenge/dns01/client_error_test.go
rename to challenge/internal/client_error_test.go
index 809b62170..0ee411b09 100644
--- a/challenge/dns01/client_error_test.go
+++ b/challenge/internal/client_error_test.go
@@ -1,4 +1,4 @@
-package dns01
+package internal
 
 import (
 	"errors"
@@ -9,9 +9,9 @@ import (
 )
 
 func TestDNSError_Error(t *testing.T) {
-	msgIn := createDNSMsg("example.com.", dns.TypeTXT, true)
+	msgIn := CreateDNSMsg("example.com.", dns.TypeTXT, true)
 
-	msgOut := createDNSMsg("example.org.", dns.TypeSOA, true)
+	msgOut := CreateDNSMsg("example.org.", dns.TypeSOA, true)
 	msgOut.Rcode = dns.RcodeNameError
 
 	testCases := []struct {
diff --git a/challenge/internal/dns.go b/challenge/internal/dns.go
new file mode 100644
index 000000000..c56b51714
--- /dev/null
+++ b/challenge/internal/dns.go
@@ -0,0 +1,15 @@
+package internal
+
+import "github.com/miekg/dns"
+
+func CreateDNSMsg(fqdn string, rtype uint16, recursive bool) *dns.Msg {
+	m := new(dns.Msg)
+	m.SetQuestion(fqdn, rtype)
+	m.SetEdns0(4096, false)
+
+	if !recursive {
+		m.RecursionDesired = false
+	}
+
+	return m
+}