diff --git a/Source/DataModel.h b/Source/DataModel.h
index 2d29c87..11926d3 100644
--- a/Source/DataModel.h
+++ b/Source/DataModel.h
@@ -7,6 +7,7 @@
 // Foundation, either version 3 of the License, or any later version.
 //

+#include <bitset>
 #import <Cocoa/Cocoa.h>

 #import "LocateDatabaseOperation.h"
@@ -14,6 +15,13 @@
 @protocol DataModelDelegate;
 @class ThreadSafeDelegate;

+enum RequiredDatabases {
+  kSMSDatabaseModel = 0,
+  kGroupedMessagesDatabaseModel,
+  kAddressBookDatabaseModel,
+  kDatabaseModelCount
+};
+
 @interface DataModel : NSObject<LocateDatabaseOperationDelegate> {
  @private
   // The path to the backup directory.
@@ -28,9 +36,12 @@
   __strong ThreadSafeDelegate<DataModelDelegate>* delegate_;

   // The lock and used when loading people from the address book.
-  BOOL groupedMessagesLoaded_;
   __strong NSCondition* peopleCondition_;

+  // A bitset reprsenting the databases of the RequiredDatabases enum that have
+  // been loaded.
+  std::bitset<kDatabaseModelCount> loadedDatabases_;
+
   // The dictionary of unique message IDs to the Message record.
   __strong NSDictionary* messageStorage_;

diff --git a/Source/DataModel.mm b/Source/DataModel.mm
index 9221cf2..814f3bd 100644
--- a/Source/DataModel.mm
+++ b/Source/DataModel.mm
@@ -34,6 +34,7 @@
                                             protocol:@protocol(DataModelDelegate)
                                               thread:[NSThread mainThread]];
     peopleCondition_ = [[NSCondition alloc] init];
+    loadedDatabases_.reset();
     [self performSelectorInBackground:@selector(locateDatabases)
                            withObject:nil];
   }
@@ -124,7 +125,8 @@
                  forKey:[row objectForKey:@"ROWID"]];
   }
   messageStorage_ = [messages retain];
-
+
+  loadedDatabases_.set(kSMSDatabaseModel);
   [delegate_ messagesLoaded];

   NSMutableDictionary* buckets = [[NSMutableDictionary alloc] init];
@@ -146,7 +148,7 @@
   }

   [peopleCondition_ lock];
-  groupedMessagesLoaded_ = YES;
+  loadedDatabases_.set(kGroupedMessagesDatabaseModel);
   groupedMessages_ = buckets;
   [peopleCondition_ signal];
   [peopleCondition_ unlock];
@@ -194,10 +196,10 @@
   // At this point, we need to have all the messages grouped by phone number,
   // so we can attach names to the PhoneNumber records.
   [peopleCondition_ lock];
-  if (!groupedMessagesLoaded_)
+  if (!loadedDatabases_.test(kGroupedMessagesDatabaseModel))
     [peopleCondition_ wait];
   [peopleCondition_ unlock];
-  assert(groupedMessagesLoaded_);
+  assert(loadedDatabases_.test(kGroupedMessagesDatabaseModel));

   // Now go through all the phone numbers, attaching names to them.
   RowReader numberReader(handle);
@@ -214,6 +216,7 @@
     record.name = name;
   }

+  loadedDatabases_.set(kAddressBookDatabaseModel);
   [delegate_ addressBookLoaded];
 }