diff --git a/src/applications/project/typeahead/PhabricatorProjectLogicalViewerDatasource.php b/src/applications/project/typeahead/PhabricatorProjectLogicalViewerDatasource.php
index e326dea254..1c472dc474 100644
--- a/src/applications/project/typeahead/PhabricatorProjectLogicalViewerDatasource.php
+++ b/src/applications/project/typeahead/PhabricatorProjectLogicalViewerDatasource.php
@@ -63,10 +63,16 @@ final class PhabricatorProjectLogicalViewerDatasource
     $phids = mpull($projects, 'getPHID');
 
     $results = array();
-    foreach ($phids as $phid) {
+    if ($phids) {
+      foreach ($phids as $phid) {
+        $results[] = new PhabricatorQueryConstraint(
+          PhabricatorQueryConstraint::OPERATOR_OR,
+          $phid);
+      }
+    } else {
       $results[] = new PhabricatorQueryConstraint(
-        PhabricatorQueryConstraint::OPERATOR_OR,
-        $phid);
+        PhabricatorQueryConstraint::OPERATOR_EMPTY,
+        null);
     }
 
     return $results;
diff --git a/src/infrastructure/query/constraint/PhabricatorQueryConstraint.php b/src/infrastructure/query/constraint/PhabricatorQueryConstraint.php
index 5b5702673b..74b3830676 100644
--- a/src/infrastructure/query/constraint/PhabricatorQueryConstraint.php
+++ b/src/infrastructure/query/constraint/PhabricatorQueryConstraint.php
@@ -7,6 +7,7 @@ final class PhabricatorQueryConstraint extends Phobject {
   const OPERATOR_NOT = 'not';
   const OPERATOR_NULL = 'null';
   const OPERATOR_ANCESTOR = 'ancestor';
+  const OPERATOR_EMPTY = 'empty';
 
   private $operator;
   private $value;
diff --git a/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php b/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
index 9996f03ae0..1892e53e7c 100644
--- a/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
+++ b/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
@@ -1872,6 +1872,16 @@ abstract class PhabricatorCursorPagedPolicyAwareQuery
       return $this;
     }
 
+    foreach ($this->edgeLogicConstraints as $type => $constraints) {
+      foreach ($constraints as $operator => $list) {
+        switch ($operator) {
+          case PhabricatorQueryConstraint::OPERATOR_EMPTY:
+            throw new PhabricatorEmptyQueryException(
+              pht('This query specifies an empty constraint.'));
+        }
+      }
+    }
+
     // This should probably be more modular, eventually, but we only do
     // project-based edge logic today.