diff --git a/src/applications/search/field/PhabricatorSearchIntField.php b/src/applications/search/field/PhabricatorSearchIntField.php
--- a/src/applications/search/field/PhabricatorSearchIntField.php
+++ b/src/applications/search/field/PhabricatorSearchIntField.php
@@ -8,7 +8,29 @@
   }
 
   protected function getValueFromRequest(AphrontRequest $request, $key) {
-    return $request->getInt($key);
+    // Use getStr() to differentiate in validateControlValue() between 0
+    // literally entered versus 0 returned by PHP casting a string to an int
+    return $request->getStr($key);
+  }
+
+  public function getValueForQuery($value) {
+    return $this->validateControlValue($value);
+  }
+
+  protected function validateControlValue($value) {
+    if ($value === null || $value === '') {
+      return $value;
+    }
+    // Handle negative number strings by stripping the minus
+    if (($value[0] === '-' || $value[0] === '\xe2\x88\x92')) {
+      $value = substr($value, 1);
+    }
+    if (ctype_digit((string)$value)) {
+      return $value;
+    }
+    $this->addError(
+      pht('Invalid'),
+      pht('Integer value for "%s" can not be parsed.', $this->getLabel()));
   }
 
   protected function newControl() {