diff --git a/api/lib/validation/schemaValidator.js b/api/lib/validation/schemaValidator.js
index 40bb18544..b13eeb5f3 100644
--- a/api/lib/validation/schemaValidator.js
+++ b/api/lib/validation/schemaValidator.js
@@ -58,11 +58,6 @@ var getDaysInMonthInISOFormat = function() {
   return monthEnum;
 };
 
-var getMetricTypes = function() {
-  var metricTypeEnum = ['memoryused', 'memoryutil', 'responsetime', 'throughput'];
-  return metricTypeEnum;
-};
-
 
 var getPolicySchema = function() {
   var schema = {
@@ -92,7 +87,7 @@ var getScalingRuleSchema = function() {
     'type': 'object',
     'id':'/scaling_rules',
     'properties' : {
-      'metric_type':{ 'type':'string' },
+      'metric_type':{ 'type':'string', 'pattern':'^[a-zA-Z0-9_]+$' },
       'breach_duration_secs':{ 'type':'integer','minimum': 60,'maximum': 3600 },
       'threshold':{ 'type':'integer'},
       'operator':{ 'type':'string','enum': validOperators },
diff --git a/api/test/unit/validation/schemaValidator.test.js b/api/test/unit/validation/schemaValidator.test.js
index 1b46c1a93..c20c69311 100644
--- a/api/test/unit/validation/schemaValidator.test.js
+++ b/api/test/unit/validation/schemaValidator.test.js
@@ -65,7 +65,7 @@ describe('Validating Policy JSON schema construction',function(){
     var validOperator = schemaValidatorPrivate.__get__('getValidOperators')();
     var adjustmentPattern = schemaValidatorPrivate.__get__('getAdjustmentPattern')();
     expect(schema.id).to.equal('/scaling_rules');
-    expect(schema.properties.metric_type).to.deep.equal({ 'type':'string' });
+    expect(schema.properties.metric_type).to.deep.equal({ 'type':'string','pattern': '^[a-zA-Z0-9_]+$' });
     expect(schema.properties.breach_duration_secs).to.deep.equal({ 'type':'integer','minimum': 60,'maximum': 3600 });
     expect(schema.properties.threshold).to.deep.equal({ 'type':'integer'});
     expect(schema.properties.operator).to.deep.equal({ 'type':'string','enum':validOperator });
diff --git a/api/test/unit/validation/validationMiddleware.test.js b/api/test/unit/validation/validationMiddleware.test.js
index 9219bd2e4..f202f4931 100644
--- a/api/test/unit/validation/validationMiddleware.test.js
+++ b/api/test/unit/validation/validationMiddleware.test.js
@@ -212,8 +212,7 @@ describe('Validate Policy JSON Schema structure', function () {
 
     var requiredProperties = schemaValidatorPrivate.__get__('getScalingRuleSchema')().required;
     var allProperties = Object.keys(schemaValidatorPrivate.__get__('getScalingRuleSchema')().properties);
-
-    var metricTypes = schemaValidatorPrivate.__get__('getMetricTypes')();
+    var validMetricTypes = ['memoryutil','memoryused','responsetime','throughput','custom_metric'];
     var validMetricThresholdSettings = [
       { metric_type: "memoryutil", thresholds: [30, 100] },
       { metric_type: "memoryused", thresholds: [30, 100, 1000] },
@@ -259,7 +258,7 @@ describe('Validate Policy JSON Schema structure', function () {
             });
         });
 
-        metricTypes.forEach(function (metricType) {
+        validMetricTypes.forEach(function (metricType) {
           it('succeed with valid metric type ' + metricType + ', policy type ' + type, function (done) {
             buildTestPolicy(fakePolicy, type);
             for (let i = 0; i < fakePolicy.scaling_rules.length; i++) {
@@ -374,10 +373,24 @@ describe('Validate Policy JSON Schema structure', function () {
               });
           });
         });
+        it('should fail with custom metric type. policy type ' + type, function (done) {
+          buildTestPolicy(fakePolicy, type);
+          fakePolicy.scaling_rules[0].metric_type = 'my metric $';
+          request(app)
+            .put('/v1/apps/fakeID/policy', validationMiddleware)
+            .send(fakePolicy)
+            .end(function (error, result) {
+              expect(result.statusCode).to.equal(400);
+              expect(result.body.error).to.not.be.null;
+              expect(result.body.error[0].message).to.equal('does not match pattern "^[a-zA-Z0-9_]+$"');
+              expect(result.body.error[0].stack).to.equal('instance.scaling_rules[0].metric_type does not match pattern "^[a-zA-Z0-9_]+$"');
+              done();
+            });
+        });
 
         it('should not fail with custom metric type. policy type ' + type, function (done) {
           buildTestPolicy(fakePolicy, type);
-          fakePolicy.scaling_rules[0].metric_type = 'custom-metric';
+          fakePolicy.scaling_rules[0].metric_type = 'custom_metric';
           request(app)
             .put('/v1/apps/fakeID/policy', validationMiddleware)
             .send(fakePolicy)
diff --git a/servicebroker/config/catalog.schema.json b/servicebroker/config/catalog.schema.json
index a94830c20..c34af4c8c 100644
--- a/servicebroker/config/catalog.schema.json
+++ b/servicebroker/config/catalog.schema.json
@@ -201,13 +201,8 @@
                   "description": "The interval between two successive scaling activity"
                 },
                 "metric_type": {
-                  "enum": [
-                    "memoryused",
-                    "memoryutil",
-                    "responsetime",
-                    "throughput"
-                  ],
-                  "type": "string"
+                  "type": "string",
+                  "pattern": "^[a-zA-Z0-9_]+$"
                 },
                 "operator": {
                   "enum": [
diff --git a/servicebroker/test/routes/catalog_test.js b/servicebroker/test/routes/catalog_test.js
index 3248e0aa3..e15381947 100644
--- a/servicebroker/test/routes/catalog_test.js
+++ b/servicebroker/test/routes/catalog_test.js
@@ -117,11 +117,16 @@ describe("Validate schema definition",function(){
       expect(ajv.validate(catalogSchema,fakePolicy)).to.be.false;
     });
 
-    it("validate metric_type",function(){
-      fakePolicy.scaling_rules[0].metric_type = "mymetrictype"
+    it("validate metric_type with non alphanumeric characters",function(){
+      fakePolicy.scaling_rules[0].metric_type = "ab cd$"
       expect(ajv.validate(catalogSchema,fakePolicy)).to.be.false;
     });
 
+    it("validate metric_type with underscore",function(){
+      fakePolicy.scaling_rules[0].metric_type = "my_metric2"
+      expect(ajv.validate(catalogSchema,fakePolicy)).to.be.true;
+    });
+
     it("validate operator",function(){
       fakePolicy.scaling_rules[0].operator = "$"
       expect(ajv.validate(catalogSchema,fakePolicy)).to.be.false;