diff --git a/configure.ac b/configure.ac
index 7e04ff5e..a859ddb6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,6 +12,7 @@ AC_DEFINE(SWIG_SHARED_OBJ)
 AC_DEFINE(PHREEQC_CPP)
 AC_DEFINE(PHREEQC_CLASS)
 AC_DEFINE(USE_PHRQ_ALLOC)
+AC_DEFINE(NDEBUG)
 
 # Checks for programs.
 AC_PROG_CC