diff --git a/src/KSPACE/pppm.cpp b/src/KSPACE/pppm.cpp
index d85e1ffa93..68b584b22e 100644
--- a/src/KSPACE/pppm.cpp
+++ b/src/KSPACE/pppm.cpp
@@ -36,8 +36,6 @@
 
 using namespace LAMMPS_NS;
 
-#undef hz                      // required by IBM AIX compiler
-
 #define MAXORDER 7
 #define OFFSET 4096
 #define SMALL 0.00001