diff --git a/m4/lx_check_cplex.m4 b/m4/lx_check_cplex.m4
--- a/m4/lx_check_cplex.m4
+++ b/m4/lx_check_cplex.m4
@@ -46,7 +46,7 @@
       #include <ilcplex/cplex.h>
       }
 
-      int main(int argc, char* argv[])
+      int main(int argc, char** argv)
       {
         CPXENVptr env = NULL;
         return 0;