diff --git a/lessc.inc.php b/lessc.inc.php
index 5c81ad2a..75bcdd4d 100644
--- a/lessc.inc.php
+++ b/lessc.inc.php
@@ -42,6 +42,7 @@ class lessc {
 	static protected $TRUE = array("keyword", "true");
 	static protected $FALSE = array("keyword", "false");
 
+	protected $allParsedFiles = array();
 	protected $libFunctions = array();
 	protected $registeredVars = array();
 	protected $preserveComments = false;
@@ -108,6 +109,11 @@ protected function tryImport($importPath, $parentBlock, $out) {
 		if ($this->importDisabled) {
 			return array(false, "/* import disabled */");
 		}
+		
+		// import once
+		if(array_key_exists(realpath($realPath), $this->allParsedFiles())) {
+			return array(false, '');
+		}
 
 		$this->addParsedFile($realPath);
 		$parser = $this->makeParser($realPath);