diff --git a/progtest/src/TestRunner.js b/progtest/src/TestRunner.js
index 5af3d4cb..ee0f4dcc 100644
--- a/progtest/src/TestRunner.js
+++ b/progtest/src/TestRunner.js
@@ -156,8 +156,8 @@ module.exports = Class( 'TestRunner',
     /**
      * Attempt test case, returning error on failure
      *
-     * If an error is thrown (e.g. terminating classification), it will be
-     * returned in place of the results.
+     * If an error is thrown (e.g. terminating classification or unknown
+     * input), then it will be returned in place of the results.
      *
      * @param {Object} data input data
      *
@@ -168,6 +168,8 @@ module.exports = Class( 'TestRunner',
         // no input map---#rate uses params directly
         try
         {
+            this._verifyKnownParams( data );
+
             return this._program.rater( data ).vars;
         }
         catch( e )
@@ -177,6 +179,33 @@ module.exports = Class( 'TestRunner',
     },
 
 
+    /**
+     * Verify that all provided inputs match known params
+     *
+     * If a given input is not known for the rater for the current program,
+     * an Error will be thrown with a comma-delimited list of all unknown
+     * params.
+     *
+     * @param {Object} data input data
+     *
+     * @return {undefined}
+     *
+     * @throws Error when unknown input is found
+     */
+    'private _verifyKnownParams'( data )
+    {
+        const params = this._program.rater.params || {};
+
+        const unknown = Object.keys( data )
+            .filter( param => params[ param ] === undefined );
+
+        if ( unknown.length > 0 )
+        {
+            throw Error( "Unknown params: " + unknown.join( ", " ) );
+        }
+    },
+
+
     /**
      * Recursively compare values (scalar, array)
      *
diff --git a/progtest/test/TestRunnerTest.js b/progtest/test/TestRunnerTest.js
index 6d88415d..75e8ed9e 100644
--- a/progtest/test/TestRunnerTest.js
+++ b/progtest/test/TestRunnerTest.js
@@ -41,6 +41,9 @@ describe( "TestRunner", () =>
             }
         };
 
+        // `a' is a known param
+        program.rater.params = { a: {} };
+
         const test_cases = [
             {
                 description: "first",
@@ -118,6 +121,32 @@ describe( "TestRunner", () =>
     } );
 
 
+    it( "fails on unknown params", () =>
+    {
+        // no params at all are defined
+        const program = { rater: () => ( { vars: {} } ) };
+
+        const bad_test = {
+            description: 'bad param',
+            data:        {
+                unknown_param_1: 0,
+                unknown_param_2: 0,
+            },
+            expect:      {},
+        };
+
+        return Sut( NullTestReporter(), program )
+            .runTests( [ bad_test ] )
+            .then( ( [ result ] ) =>
+            {
+                expect( result.failures[ 0 ].result )
+                    .to.contain( 'unknown_param_1' );
+                expect( result.failures[ 0 ].result )
+                    .to.contain( 'unknown_param_2' );
+            } );
+    } );
+
+
     it( "invokes reporter before, during, and after test cases", done =>
     {
         let pre     = false;
diff --git a/progtest/test/_stub/program.js b/progtest/test/_stub/program.js
index 3f42a984..673ce57e 100644
--- a/progtest/test/_stub/program.js
+++ b/progtest/test/_stub/program.js
@@ -23,3 +23,6 @@ exports.rater = data =>
 {
     return { vars: { out: data.in } };
 };
+
+exports.rater.params = { in: {} };
+