diff --git a/github/rules.go b/github/rules.go
index 1efb1783f92..f7ab4b613c9 100644
--- a/github/rules.go
+++ b/github/rules.go
@@ -573,9 +573,7 @@ type repositoryRulesetRuleWrapper struct {
 
 // MarshalJSON is a custom JSON marshaler for RulesetRules.
 func (r *RepositoryRulesetRules) MarshalJSON() ([]byte, error) {
-	// The RepositoryRulesetRules type marshals to between 1 and 22 rules.
-	// If new rules are added to RepositoryRulesetRules the capacity below needs increasing
-	rawRules := make([]json.RawMessage, 0, 22)
+	var rawRules []json.RawMessage
 
 	if r.Creation != nil {
 		bytes, err := marshalRepositoryRulesetRule(RulesetRuleTypeCreation, r.Creation)
@@ -793,6 +791,10 @@ func (r *RepositoryRulesetRules) MarshalJSON() ([]byte, error) {
 		rawRules = append(rawRules, json.RawMessage(bytes))
 	}
 
+	if len(rawRules) == 0 {
+		return []byte("[]"), nil
+	}
+
 	return json.Marshal(rawRules)
 }