diff --git a/Makefile b/Makefile
index b2a610a..4784f5e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,10 @@
+.PHONY: test test-unit install test-integration
+
 ROOT=$(shell pwd)
 
+install:
+	npm install
+
 test: test-unit
 
 test-unit:
@@ -12,4 +17,4 @@ test-integration:
 	ln -s $(ROOT) node_modules/sails-postgresql/node_modules/waterline-sequel
 	rm -rf node_modules/sails-mysql/node_modules/waterline-sequel
 	ln -s $(ROOT) node_modules/sails-mysql/node_modules/waterline-sequel
-	@NODE_ENV=test node test/integration/runnerDispatcher.js
\ No newline at end of file
+	@NODE_ENV=test node test/integration/runnerDispatcher.js
diff --git a/sequel/lib/criteriaProcessor.js b/sequel/lib/criteriaProcessor.js
index be2cb51..2fcffdc 100644
--- a/sequel/lib/criteriaProcessor.js
+++ b/sequel/lib/criteriaProcessor.js
@@ -830,6 +830,11 @@ CriteriaProcessor.prototype.prepareCriterion = function prepareCriterion(key, va
       }
 
       break;
+
+    default:
+      var err = new Error('Unknown filtering operator: "' + key + "\". Should be 'startsWith', '>', 'contains' or similar");
+      err.operator = key;
+      throw err;
   }
 
   // Bump paramCount
diff --git a/test/unit/index.test.js b/test/unit/index.test.js
index dce209d..c16a168 100644
--- a/test/unit/index.test.js
+++ b/test/unit/index.test.js
@@ -82,6 +82,14 @@ describe('Sequel', function () {
     });
   });
 
+  describe('queries with an unknown operator', function () {
+    it('throws an error when the operator is unknown', function() {
+      var sequel = new Sequel(schema);
+      assert.throws(sequel.find.bind(sequel, 'bar', { id: { 'in': [ 1, 2 ] } }),
+        Error, "Unknown filtering operator: \"in\". Should be 'startsWith', '>', 'contains' or similar");
+    });
+  });
+
   describe('.find() with schema name', function () {
     var _options = _.extend({}, options, {schemaName: {'foo':'myschema','oddity':'anotherschema','bat':'public'}});
     // Loop through the query objects and test them against the `.find()` method.
@@ -99,5 +107,5 @@ describe('Sequel', function () {
         done();
       });
     });
-  });  
+  });
 });