--- /dev/null
+diff --git a/configure.ac b/configure.ac
+index 466f7f9..48490df 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -145,10 +145,6 @@ CC_CHECK_CFLAGS_APPEND([-Wall -Wdisabled-optimization -Wpointer-arith ]dnl
+ [-Wredundant-decls -Wcast-qual -Wwrite-strings -Wtype-limits -Wundef ]dnl
+ [-Wmissing-prototypes -Wshadow])
+
+-CC_CHECK_CFLAGS_APPEND([-Werror=implicit-function-declaration ]dnl
+- [-Werror-implicit-function-declaration],
+- [break;])
+-
+ CC_CHECK_WERROR
+ AS_IF([test "x$enable_werror" = "xyes"], [
+ CFLAGS="${CFLAGS} $cc_cv_werror"