diff --git a/.travis.yml b/.travis.yml
index 6e96744..09b01a9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,7 +5,7 @@ language: c
 
 # treat all warnings as errors, fake cross-toolchain (build everything on host)
 env:
-  - CFLAGS=-Werror CROSS_COMPILE=""
+  - CFLAGS="-g -O2 -Werror" CROSS_COMPILE=""
 
 os:
   - linux
diff --git a/Makefile b/Makefile
index e66dd6e..65bdcdc 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 CC ?= gcc
-DEFAULT_CFLAGS := -g -O0 -Wall -Wextra -std=c99
+DEFAULT_CFLAGS := -std=c99
+DEFAULT_CFLAGS += -Wall -Wextra -Wno-unused-result
 
 DEFAULT_CFLAGS += -D_POSIX_C_SOURCE=200112L
 # Define _BSD_SOURCE, necessary to expose all endian conversions properly.