diff --git a/snippets/snippet/index.js b/snippets/snippet/index.js
index f1c156d..545c663 100644
--- a/snippets/snippet/index.js
+++ b/snippets/snippet/index.js
@@ -27,15 +27,15 @@ function run (folder, args) {
 function assert (folder, args) {
   const tests = [
     {
-      f:      () => (args.length === 1),
-      reason: 'not enough arguments'
+      f:      () => (args.length < 2),
+      reason: 'too many arguments'
     },
     {
-      f:      () => (typeof args[0] === 'string'),
+      f:      () => (args.length === 0 || typeof args[0] === 'string'),
       reason: 'name is not a string'
     },
     {
-      f:      () => (/^[a-z]+$/iu).test (args[0]),
+      f:      () => (args.length === 0 || (/^[a-z]+$/iu).test (args[0])),
       reason: 'name can only contain [a-z]'
     },
     {
@@ -44,7 +44,16 @@ function assert (folder, args) {
     },
     {
       f:      () => (fs.existsSync (folder)),
-      reason: 'cwd does not exist'
+      reason: 'cwd does not exist (internal error)'
+    },
+    {
+      f:      () => (args.length === 1 || fs.readdirSync (folder).length === 0),
+      reason: 'folder is not empty'
+    },
+    {
+      f:      () => (args.length === 0
+          || !fs.existsSync (path.join (folder, args[0]))),
+      reason: 'folder already exists'
     }
   ];
   for (const test of tests)
diff --git a/snippets/snippet/template/index.js b/snippets/snippet/template/index.js
index f1c156d..545c663 100644
--- a/snippets/snippet/template/index.js
+++ b/snippets/snippet/template/index.js
@@ -27,15 +27,15 @@ function run (folder, args) {
 function assert (folder, args) {
   const tests = [
     {
-      f:      () => (args.length === 1),
-      reason: 'not enough arguments'
+      f:      () => (args.length < 2),
+      reason: 'too many arguments'
     },
     {
-      f:      () => (typeof args[0] === 'string'),
+      f:      () => (args.length === 0 || typeof args[0] === 'string'),
       reason: 'name is not a string'
     },
     {
-      f:      () => (/^[a-z]+$/iu).test (args[0]),
+      f:      () => (args.length === 0 || (/^[a-z]+$/iu).test (args[0])),
       reason: 'name can only contain [a-z]'
     },
     {
@@ -44,7 +44,16 @@ function assert (folder, args) {
     },
     {
       f:      () => (fs.existsSync (folder)),
-      reason: 'cwd does not exist'
+      reason: 'cwd does not exist (internal error)'
+    },
+    {
+      f:      () => (args.length === 1 || fs.readdirSync (folder).length === 0),
+      reason: 'folder is not empty'
+    },
+    {
+      f:      () => (args.length === 0
+          || !fs.existsSync (path.join (folder, args[0]))),
+      reason: 'folder already exists'
     }
   ];
   for (const test of tests)