diff --git a/README.md b/README.md
index b547c72..810205c 100644
--- a/README.md
+++ b/README.md
@@ -36,10 +36,13 @@ a string or a number.
 ### If
 
 An "if:<name>" section can contain other objects, but the entirety of
-the section is only rendered if the current context scope contains the
-current name, and the value associated with that name is "true" in a
-boolean context.  You might use to show someone's name, if the name
-field is populated, and show nothing if it isn't.
+the section is only rendered if the current context scope, and *only*
+the current context scope, contains the current name, and the value
+associated with that name is "true" in a boolean context.  You might
+use to show someone's name, if the name field is populated, and show
+nothing if it isn't.  This is useful for detecting if the current
+context has a field, but you don't want previous contexts' synonyms
+showing up.
 
 If your datasource returns:
 
@@ -49,6 +52,12 @@ Then your template would use:
 
     {if:name}Hello {name}!{/if:name}
 
+### When
+
+A "when:<name>" section is the same as the "if", but it will render if
+the current context scope, and any previous context scope on the
+stack, contains the current name.
+
 ### Block
 
 A "block:<name>" section can contain other objects, but the entirety
diff --git a/lib/lexer.js b/lib/lexer.js
index e76a47c..9cc1dff 100644
--- a/lib/lexer.js
+++ b/lib/lexer.js
@@ -816,7 +816,7 @@ module.exports = (function() {
         var _VBT_LENGTH = _VALID_BLOCK_TYPES.length;
 
         function is_valid_block_type(b) {
-            for(i = 0; i < _VBT_LENGTH; i++) {
+            for(var i = 0; i < _VBT_LENGTH; i++) {
                 if (_VALID_BLOCK_TYPES[i] == b) {
                     return true;
                 }
diff --git a/lib/parser.js b/lib/parser.js
index 4501832..457bf25 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -110,8 +110,15 @@
     };
 
     Contexter.prototype.render = function(name) {
+      var ret;
       if ((this.templates[name] != null) && _.isFunction(this.templates[name])) {
-        return this.templates[name](this);
+        this.depth++;
+        if (this.depth > 10) {
+          throw new Error('recursion-error');
+        }
+        ret = this.templates[name](this);
+        this.depth--;
+        return ret;
       } else {
         return "";
       }
diff --git a/src/lexer.peg b/src/lexer.peg
index 3e6b2be..54f5a5e 100644
--- a/src/lexer.peg
+++ b/src/lexer.peg
@@ -4,7 +4,7 @@
     var _VBT_LENGTH = _VALID_BLOCK_TYPES.length;
 
     function is_valid_block_type(b) {
-        for(i = 0; i < _VBT_LENGTH; i++) {
+        for(var i = 0; i < _VBT_LENGTH; i++) {
             if (_VALID_BLOCK_TYPES[i] == b) {
                 return true;
             }
diff --git a/src/parser.coffee b/src/parser.coffee
index 7197883..eb5050d 100644
--- a/src/parser.coffee
+++ b/src/parser.coffee
@@ -71,7 +71,14 @@ class Contexter
         return ""
 
     render: (name) ->
-        if @templates[name]? and _.isFunction(@templates[name]) then @templates[name](@) else ""
+        if @templates[name]? and _.isFunction(@templates[name])
+            @depth++
+            throw new Error('recursion-error') if @depth > 10
+            ret = @templates[name](@)
+            @depth--
+            ret
+        else
+            ""
 
 
 module.exports = (ast, data) ->