diff --git a/src/calibre/library/caches.py b/src/calibre/library/caches.py
index 83c56c5395..e2ecdd9f55 100644
--- a/src/calibre/library/caches.py
+++ b/src/calibre/library/caches.py
@@ -241,6 +241,24 @@ class ResultCache(SearchQueryParser):
         matches = set([])
         if len(query) < 2:
             return matches
+
+        if location == 'date':
+            location = 'timestamp'
+        loc = self.field_metadata[location]['rec_index']
+
+        if query == 'false':
+            for item in self._data:
+                if item is None: continue
+                if item[loc] is None or item[loc] == UNDEFINED_DATE:
+                    matches.add(item[0])
+            return matches
+        if query == 'true':
+            for item in self._data:
+                if item is None: continue
+                if item[loc] is not None and item[loc] != UNDEFINED_DATE:
+                    matches.add(item[0])
+            return matches
+
         relop = None
         for k in self.date_search_relops.keys():
             if query.startswith(k):
@@ -249,10 +267,6 @@ class ResultCache(SearchQueryParser):
         if relop is None:
                 (p, relop) = self.date_search_relops['=']
 
-        if location == 'date':
-            location = 'timestamp'
-        loc = self.field_metadata[location]['rec_index']
-
         if query == _('today'):
             qd = now()
             field_count = 3
@@ -301,7 +315,7 @@ class ResultCache(SearchQueryParser):
         if query == 'false':
             query = '0'
         elif query == 'true':
-            query = '>0'
+            query = '!=0'
         relop = None
         for k in self.numeric_search_relops.keys():
             if query.startswith(k):