diff --git a/spec/ameba/rule/lint/syntax_spec.cr b/spec/ameba/rule/lint/syntax_spec.cr
index 52c7cabe..f7402e76 100644
--- a/spec/ameba/rule/lint/syntax_spec.cr
+++ b/spec/ameba/rule/lint/syntax_spec.cr
@@ -33,5 +33,9 @@ module Ameba::Rule::Lint
       issue.location.to_s.should eq "source.cr:1:11"
       issue.message.should eq "unexpected token: end (expected ';' or newline)"
     end
+
+    it "has highest severity" do
+      subject.severity.should eq Severity::Error
+    end
   end
 end
diff --git a/spec/ameba/severity_spec.cr b/spec/ameba/severity_spec.cr
index 275d5059..db77d197 100644
--- a/spec/ameba/severity_spec.cr
+++ b/spec/ameba/severity_spec.cr
@@ -2,12 +2,6 @@ require "../spec_helper"
 
 module Ameba
   describe Severity do
-    describe ".default" do
-      it "returns default severity" do
-        Severity.default.should eq Severity::Refactoring
-      end
-    end
-
     describe ".from_name" do
       it "creates error severity by name" do
         Severity.from_name("Error").should eq Severity::Error
@@ -31,46 +25,60 @@ module Ameba
 
   struct SeverityConvertable
     YAML.mapping(
-      severity: { type: Severity, converter: SeverityYamlConverter }
+      severity: {type: Severity, converter: SeverityYamlConverter}
     )
   end
 
   describe SeverityYamlConverter do
     describe ".from_yaml" do
       it "converts from yaml to Severity::Error" do
-        yaml = { severity: "error" }.to_yaml
+        yaml = {severity: "error"}.to_yaml
         converted = SeverityConvertable.from_yaml(yaml)
         converted.severity.should eq Severity::Error
       end
 
       it "converts from yaml to Severity::Warning" do
-        yaml = { severity: "warning" }.to_yaml
+        yaml = {severity: "warning"}.to_yaml
         converted = SeverityConvertable.from_yaml(yaml)
         converted.severity.should eq Severity::Warning
       end
 
       it "converts from yaml to Severity::Refactoring" do
-        yaml = { severity: "refactoring" }.to_yaml
+        yaml = {severity: "refactoring"}.to_yaml
         converted = SeverityConvertable.from_yaml(yaml)
         converted.severity.should eq Severity::Refactoring
       end
+
+      it "raises if severity is not a scalar" do
+        yaml = {severity: {refactoring: true}}.to_yaml
+        expect_raises(Exception, "Severity must be a scalar") do
+          SeverityConvertable.from_yaml(yaml)
+        end
+      end
+
+      it "raises if severity has a wrong type" do
+        yaml = {severity: [1, 2, 3]}.to_yaml
+        expect_raises(Exception, "Severity must be a scalar") do
+          SeverityConvertable.from_yaml(yaml)
+        end
+      end
     end
 
     describe ".to_yaml" do
       it "converts Severity::Error to yaml" do
-        yaml = { severity: "error" }.to_yaml
+        yaml = {severity: "error"}.to_yaml
         converted = SeverityConvertable.from_yaml(yaml).to_yaml
         converted.should eq "---\nseverity: Error\n"
       end
 
       it "converts Severity::Warning to yaml" do
-        yaml = { severity: "warning" }.to_yaml
+        yaml = {severity: "warning"}.to_yaml
         converted = SeverityConvertable.from_yaml(yaml).to_yaml
         converted.should eq "---\nseverity: Warning\n"
       end
 
       it "converts Severity::Refactoring to yaml" do
-        yaml = { severity: "refactoring" }.to_yaml
+        yaml = {severity: "refactoring"}.to_yaml
         converted = SeverityConvertable.from_yaml(yaml).to_yaml
         converted.should eq "---\nseverity: Refactoring\n"
       end
diff --git a/src/ameba/config.cr b/src/ameba/config.cr
index e8fdac23..6150a6ad 100644
--- a/src/ameba/config.cr
+++ b/src/ameba/config.cr
@@ -227,6 +227,11 @@ class Ameba::Config
         {% properties["enabled".id] = {key: "Enabled", default: true, type: Bool} %}
       {% end %}
 
+      {% if properties["severity".id] == nil %}
+        {% default = @type.name.starts_with?("Ameba::Rule::Lint") ? "Severity::Warning".id : "Severity::Refactoring".id %}
+        {% properties["severity".id] = {key: "Severity", default: default, type: Severity, converter: SeverityYamlConverter} %}
+      {% end %}
+
       {% if properties["excluded".id] == nil %}
         {% properties["excluded".id] = {key: "Excluded", type: "Array(String)?".id} %}
       {% end %}
diff --git a/src/ameba/rule/lint/syntax.cr b/src/ameba/rule/lint/syntax.cr
index 070476ae..f5c2addc 100644
--- a/src/ameba/rule/lint/syntax.cr
+++ b/src/ameba/rule/lint/syntax.cr
@@ -20,7 +20,10 @@ module Ameba::Rule::Lint
   # ```
   #
   struct Syntax < Base
-    getter description = "Reports invalid Crystal syntax."
+    properties do
+      description "Reports invalid Crystal syntax"
+      severity Severity::Error
+    end
 
     def test(source)
       source.ast
diff --git a/src/ameba/severity.cr b/src/ameba/severity.cr
index 66de0763..e826901d 100644
--- a/src/ameba/severity.cr
+++ b/src/ameba/severity.cr
@@ -4,10 +4,6 @@ module Ameba
     Warning
     Refactoring
 
-    def self.default
-      Refactoring
-    end
-
     def self.from_name(name : String)
       case name.downcase
       when "error"
@@ -37,7 +33,7 @@ module Ameba
     end
 
     def self.to_yaml(value : Severity, yaml : YAML::Nodes::Builder)
-      yaml.scalar value.to_s
+      yaml.scalar value
     end
   end
 end