diff --git a/NXDNConvolution.cpp b/NXDNConvolution.cpp
index 2784a42..d74fe2a 100755
--- a/NXDNConvolution.cpp
+++ b/NXDNConvolution.cpp
@@ -21,7 +21,7 @@
 #include <cstdio>
 #include <cassert>
 #include <cstring>
-#include <cmath>
+#include <cstdlib>
 
 const unsigned char BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};