diff --git a/core/dbobjectsearch.class.php b/core/dbobjectsearch.class.php
index 50f674758..4ae238ba6 100644
--- a/core/dbobjectsearch.class.php
+++ b/core/dbobjectsearch.class.php
@@ -521,21 +521,6 @@ class DBObjectSearch extends DBSearch
 		$this->AddConditionExpression($oInCondition);
 	}
 
-	/**
-	 * @return string a unique param name
-	 */
-	private function GenerateUniqueParamName() {
-		$iExistingParamsNb = count($this->m_aParams);
-		$iCurrentArrayParamNb = $iExistingParamsNb + 1;
-		$sParamName = 'param'.$iCurrentArrayParamNb;
-
-		if (isset($this->m_aParams[$sParamName])) {
-			$sParamName .= '_'.microtime(true) . '_' .rand(0,100);
-		}
-
-		return $sParamName;
-	}
-
 	/**
 	 * Specify a condition on external keys or link sets
 	 * @param string $sAttSpec Can be either an attribute code or extkey->[sAttSpec] or linkset->[sAttSpec] and so on, recursively
diff --git a/core/dbsearch.class.php b/core/dbsearch.class.php
index e748ac1d5..6fa47c20e 100644
--- a/core/dbsearch.class.php
+++ b/core/dbsearch.class.php
@@ -726,6 +726,15 @@ abstract class DBSearch
 	 */
 	public abstract function GetCriteria();
 
+	public abstract function AddConditionForInOperatorUsingParam($sFilterCode, $aValues, $bPositiveMatch = true);
+
+	/**
+	 * @return string a unique param name
+	 */
+	protected function GenerateUniqueParamName() {
+		return str_replace('.', '', 'param_'.microtime(true).rand(0,100));
+	}
+
 	////////////////////////////////////////////////////////////////////////////
 	//
 	// Cache/Trace/Log queries
diff --git a/core/dbunionsearch.class.php b/core/dbunionsearch.class.php
index 2fe7f60b2..597e2f746 100644
--- a/core/dbunionsearch.class.php
+++ b/core/dbunionsearch.class.php
@@ -628,4 +628,22 @@ class DBUnionSearch extends DBSearch
 			$oSearch->SetDataFiltered();
 		}
 	}
+
+	public function AddConditionForInOperatorUsingParam($sFilterCode, $aValues, $bPositiveMatch = true)
+	{
+		$sInParamName = $this->GenerateUniqueParamName();
+		foreach ($this->aSearches as $iSearchIndex => $oSearch)
+		{
+			$oFieldExpression = new FieldExpression($sFilterCode, $oSearch->GetClassAlias());
+
+			$sOperator = $bPositiveMatch ? 'IN' : 'NOT IN';
+
+			$oParamExpression = new VariableExpression($sInParamName);
+			$oSearch->GetInternalParamsByRef()[$sInParamName] = $aValues;
+
+			$oListExpression = new ListExpression(array($oParamExpression));
+			$oInCondition = new BinaryExpression($oFieldExpression, $sOperator, $oListExpression);
+			$oSearch->AddConditionExpression($oInCondition);
+		}
+	}
 }