diff --git a/nabo/kdtree_cpu.cpp b/nabo/kdtree_cpu.cpp
index cb1f8d1..a54b99f 100644
--- a/nabo/kdtree_cpu.cpp
+++ b/nabo/kdtree_cpu.cpp
@@ -31,6 +31,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "nabo_private.h"
 #include "index_heap.h"
+#include <cassert>
 #include <iostream>
 #include <stdexcept>
 #include <limits>