diff --git a/src/storage.cr b/src/storage.cr
index e2c8576..82e2f87 100644
--- a/src/storage.cr
+++ b/src/storage.cr
@@ -221,8 +221,7 @@ class DNSManager::Storage
 
 		zone << rr
 
-		# Update the zone.
-		zones_by_domain.update_or_create zone.domain, zone
+		update_zone zone
 
 		Response::RRAdded.new zone.domain, rr
 	rescue e
@@ -230,6 +229,13 @@ class DNSManager::Storage
 		Response::Error.new "error while adding a resource record in domain #{domain}"
 	end
 
+	# Any modification of the zone must be performed here.
+	# This function updates the SOA serial before storing the modified zone.
+	def update_zone(zone : Zone)
+		zone.update_serial
+		zones_by_domain.update_or_create zone.domain, zone
+	end
+
 	def update_rr(user_id : Int32, domain : String, rr : Zone::ResourceRecord) : IPC::JSON
 		# User must exist.
 		user_data = user_data_by_uid.get? user_id.to_s
@@ -269,8 +275,7 @@ class DNSManager::Storage
 
 		zone.resources = zone.resources.map { |x| x.rrid == rr.rrid ? rr : x }
 
-		# Update the zone.
-		zones_by_domain.update_or_create zone.domain, zone
+		update_zone zone
 
 		Response::RRUpdated.new domain, rr
 	rescue e
@@ -298,8 +303,7 @@ class DNSManager::Storage
 
 		zone.resources.select! { |x| x.rrid != rrid }
 
-		# Update the zone.
-		zones_by_domain.update_or_create zone.domain, zone
+		update_zone zone
 
 		Response::RRDeleted.new rrid
 	rescue e
diff --git a/src/storage/zone.cr b/src/storage/zone.cr
index ece98a7..d3b2c6f 100644
--- a/src/storage/zone.cr
+++ b/src/storage/zone.cr
@@ -594,6 +594,15 @@ class DNSManager::Storage::Zone
 		end
 	end
 
+	def update_serial
+		@resources.each do |rr|
+			case rr
+			when SOA
+				rr.serial += 1
+			end
+		end
+	end
+
 	def get_errors? : Array(Error)?
 		errors = [] of Error
 		unless Zone.is_domain_valid? @domain