diff --git a/src/generators/comba_mult_gen.c b/src/generators/comba_mult_gen.c
index 97ad8cd..30fe7b2 100644
--- a/src/generators/comba_mult_gen.c
+++ b/src/generators/comba_mult_gen.c
@@ -10,6 +10,7 @@
 
 /* program emits a NxN comba multiplier */
 #include <stdio.h>
+#include <stdlib.h>
 
 int main(int argc, char **argv)
 {