diff --git a/lib/bem.jade b/lib/bem.jade
index 8f888ce..e5d8caf 100644
--- a/lib/bem.jade
+++ b/lib/bem.jade
@@ -24,7 +24,8 @@ mixin b(options)
 
     //- Catch the bemto block
     if bemto_classes.length
-      - var bemto_block = bemto_classes[0].match(new RegExp('^(((?!' + bemto_settings['element'] + '|' + bemto_settings['modifier'] +').)+)'))[1]
+      - var bemto_block = bemto_classes[0].match(new RegExp('^(((?!' + bemto_settings['element'] + '|' + bemto_settings['modifier'] +').)+)'))
+      - bemto_block = bemto_block && bemto_block[1]
 
     if !isElement
       - bemto_chain[bemto_chain.length] = bemto_block
@@ -32,30 +33,31 @@ mixin b(options)
     else if bemto_classes.length && bemto_chain[bemto_chain.length-1]
       - bemto_classes[0] = bemto_chain[bemto_chain.length-1] + bemto_settings['element'] + bemto_classes[0]
 
-    - var current_block = (isElement ? bemto_chain[bemto_chain.length-1] + bemto_settings['element'] : '') + bemto_block
+    if bemto_block
+      - var current_block = (isElement ? bemto_chain[bemto_chain.length-1] + bemto_settings['element'] : '') + bemto_block
 
-    //- Adding the block if there is only modifier
-    - var has_modifier = false
-    each klass in bemto_classes
-      if klass && klass.match(new RegExp('^' + current_block + '(?!' + bemto_settings['element'] + '[A-Za-z]' + ')' + bemto_settings['modifier'] + '[A-Za-z]'))
-        - has_modifier = true
-    if bemto_classes.indexOf(current_block) === -1 && has_modifier
-      - bemto_classes[bemto_classes.length] = current_block
+      //- Adding the block if there is only modifier
+      - var has_modifier = false
+      each klass in bemto_classes
+        if klass.match(new RegExp('^' + current_block + '(?!' + bemto_settings['element'] + '[A-Za-z]' + ')' + bemto_settings['modifier'] + '[A-Za-z]'))
+          - has_modifier = true
+      if bemto_classes.indexOf(current_block) === -1 && has_modifier
+        - bemto_classes[bemto_classes.length] = current_block
 
-    each klass, i in bemto_classes
-      if klass && klass.match(new RegExp('^(?!' + bemto_settings['element'] + ')' + bemto_settings['modifier']))
-        //- Expanding the modifiers
-        - bemto_classes[i] = current_block + klass
-      else if klass && klass.match(new RegExp('^' + bemto_settings['element']))
-        //- Expanding the mixed in elements
-        if bemto_chain[bemto_chain.length-2]
-          - bemto_classes[i] = bemto_chain[bemto_chain.length-2] + klass
-        else
-          - bemto_classes[i] = bemto_chain[bemto_chain.length-1] + klass
+      each klass, i in bemto_classes
+        if klass.match(new RegExp('^(?!' + bemto_settings['element'] + ')' + bemto_settings['modifier']))
+          //- Expanding the modifiers
+          - bemto_classes[i] = current_block + klass
+        else if klass.match(new RegExp('^' + bemto_settings['element']))
+          //- Expanding the mixed in elements
+          if bemto_chain[bemto_chain.length-2]
+            - bemto_classes[i] = bemto_chain[bemto_chain.length-2] + klass
+          else
+            - bemto_classes[i] = bemto_chain[bemto_chain.length-1] + klass
 
-      //- Adding prefixes
-      if bemto_classes[i] && bemto_classes[i].match(new RegExp('^' + current_block + '($|(?=' + bemto_settings['element'] + '|' + bemto_settings['modifier'] + '))'))
-        - bemto_classes[i] = bemto_settings['prefix'] + bemto_classes[i]
+        //- Adding prefixes
+        if bemto_classes[i] && bemto_classes[i].match(new RegExp('^' + current_block + '($|(?=' + bemto_settings['element'] + '|' + bemto_settings['modifier'] + '))'))
+          - bemto_classes[i] = bemto_settings['prefix'] + bemto_classes[i]
 
     //- Write modified classes to attributes in the correct order
     - attributes.class = bemto_classes.sort().join(' ')
diff --git a/test/cases/1_basics.html b/test/cases/1_basics.html
index dc6bcfa..286e6f8 100644
--- a/test/cases/1_basics.html
+++ b/test/cases/1_basics.html
@@ -31,3 +31,11 @@
   <bar>foo
   </bar>
 </foo>
+<div class="_">
+  <div class="lol">
+  </div>
+</div>
+<div class="_mod">
+  <div class="lol">
+  </div>
+</div>
diff --git a/test/cases/1_basics.jade b/test/cases/1_basics.jade
index dd86938..779f590 100644
--- a/test/cases/1_basics.jade
+++ b/test/cases/1_basics.jade
@@ -29,3 +29,9 @@ p
 
 +b.FOO
   +e.BAR foo
+
++b._
+  +e.lol
+
++b._mod
+  +e.lol