diff --git a/pkg/provider/acme/provider.go b/pkg/provider/acme/provider.go
index 3b4c6d8458..47e3d731d8 100644
--- a/pkg/provider/acme/provider.go
+++ b/pkg/provider/acme/provider.go
@@ -552,8 +552,11 @@ func (p *Provider) resolveDefaultCertificate(ctx context.Context, domains []stri
 
 	p.resolvingDomainsMutex.Lock()
 
-	sort.Strings(domains)
-	domainKey := strings.Join(domains, ",")
+	sortedDomains := make([]string, len(domains))
+	copy(sortedDomains, domains)
+	sort.Strings(sortedDomains)
+
+	domainKey := strings.Join(sortedDomains, ",")
 
 	if _, ok := p.resolvingDomains[domainKey]; ok {
 		p.resolvingDomainsMutex.Unlock()
@@ -947,12 +950,14 @@ func (p *Provider) certExists(validDomains []string) bool {
 	p.certificatesMu.RLock()
 	defer p.certificatesMu.RUnlock()
 
-	sort.Strings(validDomains)
+	sortedDomains := make([]string, len(validDomains))
+	copy(sortedDomains, validDomains)
+	sort.Strings(sortedDomains)
 
 	for _, cert := range p.certificates {
 		domains := cert.Certificate.Domain.ToStrArray()
 		sort.Strings(domains)
-		if reflect.DeepEqual(domains, validDomains) {
+		if reflect.DeepEqual(domains, sortedDomains) {
 			return true
 		}
 	}