diff --git a/configure.ac b/configure.ac
index b89c046c..ba82eb15 100644
--- a/configure.ac
+++ b/configure.ac
@@ -104,6 +104,9 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([char foo;])],
 CFLAGS="$saved_CFLAGS"
 AC_SUBST(SYMBOL_VISIBILITY)
 
+CPPFLAGS="$CPPFLAGS -Wall"
+CFLAGS="$CFLAGS -Wall"
+
 AX_CHECK_COMPILE_FLAG([-Werror=implicit], [CFLAGS="$CFLAGS -Werror=implicit"])
 AX_CHECK_COMPILE_FLAG([-Werror=maybe-uninitialized], [CFLAGS="$CFLAGS -Werror=maybe-uninitialized"])
 AX_CHECK_COMPILE_FLAG([-Werror=memset-transposed-args], [CFLAGS="$CFLAGS -Werror=memset-transposed-args"])