diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index 7a8c4d0..3e85655 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -465,7 +465,16 @@ class Module #:nodoc:
   # Use const_missing to autoload associations so we don't have to
   # require_association when using single-table inheritance.
   def const_missing(class_id)
-    ActiveSupport::Dependencies.load_missing_constant self, class_id
+    c = Thread.critical
+    Thread.critical = true
+    begin
+      const = ActiveSupport::Dependencies.load_missing_constant self, class_id
+    rescue
+      Thread.critical = c       
+      raise
+    end
+    Thread.critical = c
+    const
   end
 
   def unloadable(const_desc = self)
@@ -476,23 +485,32 @@ end
 
 class Class
   def const_missing(const_name)
-    if [Object, Kernel].include?(self) || parent == self
-      super
-    else
-      begin
+    c = Thread.critical
+    Thread.critical = true
+    begin
+      if [Object, Kernel].include?(self) || parent == self
+        const = super
+      else
         begin
-          ActiveSupport::Dependencies.load_missing_constant self, const_name
-        rescue NameError
-          parent.send :const_missing, const_name
+          begin
+            const = ActiveSupport::Dependencies.load_missing_constant self, const_name
+          rescue NameError
+            const = parent.send :const_missing, const_name
+          end
+        rescue NameError => e
+          # Make sure that the name we are missing is the one that caused the error
+          parent_qualified_name = ActiveSupport::Dependencies.qualified_name_for parent, const_name
+          raise unless e.missing_name? parent_qualified_name
+          qualified_name = ActiveSupport::Dependencies.qualified_name_for self, const_name
+          raise NameError.new("uninitialized constant #{qualified_name}").copy_blame!(e)
         end
-      rescue NameError => e
-        # Make sure that the name we are missing is the one that caused the error
-        parent_qualified_name = ActiveSupport::Dependencies.qualified_name_for parent, const_name
-        raise unless e.missing_name? parent_qualified_name
-        qualified_name = ActiveSupport::Dependencies.qualified_name_for self, const_name
-        raise NameError.new("uninitialized constant #{qualified_name}").copy_blame!(e)
       end
+    rescue
+      Thread.critical = c
+      raise
     end
+    Thread.critical = c
+    const
   end
 end