diff --git a/duodecimal.py b/BaseConverter.py
similarity index 98%
rename from duodecimal.py
rename to BaseConverter.py
index be774ca..9b3e51f 100644
--- a/duodecimal.py
+++ b/BaseConverter.py
@@ -95,8 +95,8 @@ class BaseConverter:
         else:
             sign = 1
             
-        if set(string) > set(digits):
-            invalid = set(string) - set(digits)
+        if set(string) > set(digits+'.'):
+            invalid = set(string) - set(digits+'.')
             raise ValueError('invalid character'.format(invalid))
         
         if '.' in string:
diff --git a/example_usage.ipynb b/example_usage.ipynb
index f06c7b6..f34d928 100644
--- a/example_usage.ipynb
+++ b/example_usage.ipynb
@@ -12,10 +12,12 @@
   {
    "cell_type": "code",
    "execution_count": 1,
-   "metadata": {},
+   "metadata": {
+    "collapsed": true
+   },
    "outputs": [],
    "source": [
-    "from duodecimal import BaseConverter, duo, binary"
+    "from BaseConverter import BaseConverter, duo, binary"
    ]
   },
   {
@@ -208,7 +210,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
@@ -217,7 +219,7 @@
        "1010(base2)"
       ]
      },
-     "execution_count": 9,
+     "execution_count": 2,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -228,7 +230,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 26,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {
@@ -237,7 +239,7 @@
        "False"
       ]
      },
-     "execution_count": 26,
+     "execution_count": 3,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -248,7 +250,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -257,7 +259,7 @@
        "'42'"
       ]
      },
-     "execution_count": 31,
+     "execution_count": 4,
      "metadata": {},
      "output_type": "execute_result"
     }