diff --git a/configure.ac b/configure.ac
index f358684e5..8b0600148 100644
--- a/configure.ac
+++ b/configure.ac
@@ -581,7 +581,7 @@ if test "$ENABLED_STACKSIZE" = "yes"
 then
     AC_CHECK_FUNC([posix_memalign], [], [AC_MSG_ERROR(stacksize needs posix_memalign)])
     AC_CHECK_FUNC([pthread_attr_setstack], [], [AC_MSG_ERROR(stacksize needs pthread_attr_setstack)])
-    AM_CFLAGS="$AM_CFLAGS -DHAVE_STACK_SIZE -DTFM_TIMING_RESISTANT"
+    AM_CFLAGS="$AM_CFLAGS -DHAVE_STACK_SIZE -DCYASSL_LOW_MEMORY"
 fi
 
 
diff --git a/cyassl/ctaocrypt/settings.h b/cyassl/ctaocrypt/settings.h
index 76462c182..ae05cd0c6 100644
--- a/cyassl/ctaocrypt/settings.h
+++ b/cyassl/ctaocrypt/settings.h
@@ -226,8 +226,11 @@
 #endif
 
 #ifdef CYASSL_LOW_MEMORY
+    #undef  RSA_LOW_MEM
     #define RSA_LOW_MEM
+    #undef  CYASSL_SMALL_STACK
     #define CYASSL_SMALL_STACK
+    #undef  TFM_TIMING_RESISTANT
     #define TFM_TIMING_RESISTANT
 #endif