--- powermanga-0.91/configure.ac
+++ powermanga-0.91/configure.ac
@@ -54,7 +54,7 @@
   AC_DEFINE(USE_MALLOC_WRAPPER, 1, Define to use a malloc wrapper)
   CFLAGS="-Wall -Werror -pedantic -Wextra -std=gnu99 -g"
 else
-  CFLAGS="-O3 -Werror -Wall -pedantic -Wextra -std=gnu99"
+  CFLAGS="$CFLAGS -Wall -Wextra -std=gnu99"
 fi
 
 dnl  Check for SDL_mixer