diff --git a/debian/changelog b/debian/changelog
index a99826df..d148c3db 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+llvm-toolchain-4.0 (1:4.0.1-6) UNRELEASED; urgency=medium
+
+  * Add NDEBUG macro, lost in the -g -> -g1 change.
+
+ -- Gianfranco Costamagna <locutusofborg@debian.org>  Mon, 25 Sep 2017 10:26:11 +0200
+
 llvm-toolchain-4.0 (1:4.0.1-5) unstable; urgency=medium
 
   * Backport of an arm patch for rust.
diff --git a/debian/rules b/debian/rules
index 2ed54831..a5d4a653 100755
--- a/debian/rules
+++ b/debian/rules
@@ -61,10 +61,13 @@ endif
 export CC=gcc-$(GCC_VERSION)
 export CXX=g++-$(GCC_VERSION)
 
-opt_flags = -g -O2
+opt_flags = -O2 -DNDEBUG
 ifneq (,$(filter $(DEB_HOST_ARCH),amd64 arm64 ppc64el s390x))
-  opt_flags = -g1 -O2
+  opt_flags += -g1
+else
+  opt_flags += -g
 endif
+
 ifneq (,$(findstring $(DEB_HOST_ARCH),armel))
   opt_flags += -marm
   # 3.8 fails to build, disable the compiler_rt builtins