diff --git a/lib/alt.js b/lib/alt.js
index d363f7c..04e7946 100644
--- a/lib/alt.js
+++ b/lib/alt.js
@@ -1,6 +1,7 @@
 const _ = require('lodash');
 
 const testcheck = require('testcheck');
+const tcg = testcheck.gen;
 
 const {gen} = require('./gen');
 const isValid = require('./isValid');
@@ -9,13 +10,13 @@ function alt(...predicates) {
     const pairs = _.chunk(predicates, 2);
     
     return {
-        conform: values => {
-            const found = _.find(pairs, ([, predicate]) => isValid(predicate, values[0]));
-            return _.isUndefined(found) ? null : [found[0], values[0]];
+        conform: ([value]) => {
+            const found = _.find(pairs, ([, predicate]) => isValid(predicate, value));
+            return _.isUndefined(found) ? null : [found[0], value];
         },
-        gen: () => testcheck.gen.bind(testcheck.gen.null, () => {
+        gen: () => tcg.bind(tcg.null, () => {
             const result = gen(_.sample(pairs)[1]);
-            return testcheck.gen.array(result, 1);
+            return tcg.array(result, 1);
         })
     };
 }
diff --git a/lib/conform.js b/lib/conform.js
index 2e43d07..e8ec27f 100644
--- a/lib/conform.js
+++ b/lib/conform.js
@@ -5,13 +5,15 @@ const {getSpec} = require('./def');
 const invalidString = ':node.spec/invalid';
 
 function conform(spec, value) {
+
     if (_.isFunction(spec)) {
         const result = spec(value);
         return result ? value : invalidString;
     } else {
         const predicate = getSpec(spec).conform;
-        
+
         const result = predicate(value);
+        
         if (_.isBoolean(result)) {
             return result ? value : invalidString;
         } else {
diff --git a/test/alt.js b/test/alt.js
index c34f411..46e7bb5 100644
--- a/test/alt.js
+++ b/test/alt.js
@@ -23,15 +23,13 @@ describe('Test the alt function', () => {
         expect(s.conform('::bool-or-string', ['foo'])).to.eql([':s', 'foo']);
     });
 
-    xit('should handle list of values', () => {
-        s.def('::opt', s.cat(':prop', isString,
-                             ':val', s.alt(':s', isString, ':b', isBoolean)));
-        expect(s.conform('::opt', ['-verbose', true])).to.eql({':prop': '-verbose', ':val': [':b', true]});
+    it('should handle list of values', () => {
+        s.def('::opt', s.cat(':prop', isString, ':val', '::bool-or-string'));
+        expect(s.conform('::opt', ['-verbose', [true]])).to.eql({':prop': '-verbose', ':val': [':b', true]});
     });
 
     xit('should handle list of values', () => {
-        s.def('::config', s.star(s.cat(':prop', isString,
-                                       ':val', s.alt(':s', isString, ':b', isBoolean))));
+        s.def('::config', s.star(s.cat(':prop', isString,':val', '::bool-or-string')));
         expect(s.conform('::config', ['-server', 'foo', '-verbose', true, 'user', 'joe'])).to.eql([]);
     });
 
diff --git a/test/cat.js b/test/cat.js
index 8ed725b..3f0364a 100644
--- a/test/cat.js
+++ b/test/cat.js
@@ -23,6 +23,11 @@ describe('Test the cat function', () => {
         expect(s.conform('::ingredient', [2, ':teaspoon'])).to.eql({':quantity': 2, ':unit': ':teaspoon'});
     });
 
+    it('should handle nested concatenation', () => {
+        s.def('::named-ingredient', s.cat(':name', isString, ':ingredient', '::ingredient'));
+        expect(s.isValid('::named-ingredient', ['salt', [2, 'teaspoon']])).to.be.true;
+    });
+    
     it('should implement a generator', () => {
         s.def('::ingredient', s.cat(':quantity', isInteger, ':unit', isString));