diff --git a/pkg/engine/validate/common.go b/pkg/engine/validate/common.go
index 9009da7c03..e9185f742c 100644
--- a/pkg/engine/validate/common.go
+++ b/pkg/engine/validate/common.go
@@ -5,8 +5,12 @@ import (
 	"strconv"
 )
 
-// convertToString converts value to string
-func convertToString(value interface{}) (string, error) {
+// convertNumberToString converts value to string
+func convertNumberToString(value interface{}) (string, error) {
+	if value == nil {
+		return "0", nil
+	}
+
 	switch typed := value.(type) {
 	case string:
 		return string(typed), nil
@@ -17,7 +21,7 @@ func convertToString(value interface{}) (string, error) {
 	case int:
 		return strconv.Itoa(typed), nil
 	default:
-		return "", fmt.Errorf("Could not convert %T to string", value)
+		return "", fmt.Errorf("could not convert %v to string", typed)
 	}
 }
 
diff --git a/pkg/engine/validate/pattern.go b/pkg/engine/validate/pattern.go
index 7e2edf23ae..7190ebff62 100644
--- a/pkg/engine/validate/pattern.go
+++ b/pkg/engine/validate/pattern.go
@@ -224,7 +224,7 @@ func validateString(log logr.Logger, value interface{}, pattern string, operator
 // validateNumberWithStr compares quantity if pattern type is quantity
 //  or a wildcard match to pattern string
 func validateNumberWithStr(log logr.Logger, value interface{}, pattern string, operator operator.Operator) bool {
-	typedValue, err := convertToString(value)
+	typedValue, err := convertNumberToString(value)
 	if err != nil {
 		log.Error(err, "failed to convert to string")
 		return false