diff --git a/library/ComponentLabeling.cpp b/library/ComponentLabeling.cpp
index 5495693..e83682a 100644
--- a/library/ComponentLabeling.cpp
+++ b/library/ComponentLabeling.cpp
@@ -454,6 +454,7 @@ myCompLabelerGroup::~myCompLabelerGroup()
 
 void myCompLabelerGroup::set( int nThreads, Mat binIm )
 {
+	CV_Assert(nThreads > 0);
 	this->numThreads=nThreads;
 	if(binIm.isContinuous()){
 		this->img=binIm;