Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -173,19 +173,21 @@
 AX_CHECK_COMPILER_FLAGS(-fno-common, [OBJCFLAGS="$OBJCFLAGS -fno-common"])
 AX_CHECK_COMPILER_FLAGS(-fno-constant-cfstrings, [
 	OBJCFLAGS="$OBJCFLAGS -fno-constant-cfstrings"
 	AC_SUBST(NO_CONST_CFSTRINGS, "-fno-constant-cfstrings")
 ])
-AX_CHECK_COMPILER_FLAGS(-Wsign-compare -Werror,
+AX_CHECK_COMPILER_FLAGS([-Wsign-compare -Werror],
 	[OBJCFLAGS="$OBJCFLAGS -Wsign-compare"])
-AX_CHECK_COMPILER_FLAGS(-Wshorten-64-to-32 -Werror,
+AX_CHECK_COMPILER_FLAGS([-Wshorten-64-to-32 -Werror],
 	[OBJCFLAGS="$OBJCFLAGS -Wshorten-64-to-32"])
-AX_CHECK_COMPILER_FLAGS(-Wsemicolon-before-method-body -Werror,
+AX_CHECK_COMPILER_FLAGS([-Wundeclared-selector -Werror],
+	[OBJCFLAGS="$OBJCFLAGS -Wundeclared-selector"])
+AX_CHECK_COMPILER_FLAGS([-Wsemicolon-before-method-body -Werror],
 	[OBJCFLAGS="$OBJCFLAGS -Wsemicolon-before-method-body"])
-AX_CHECK_COMPILER_FLAGS(-Wobjc-missing-property-synthesis -Werror,
+AX_CHECK_COMPILER_FLAGS([-Wobjc-missing-property-synthesis -Werror],
 	[OBJCFLAGS="$OBJCFLAGS -Wobjc-missing-property-synthesis"])
-AX_CHECK_COMPILER_FLAGS(-Watomic-properties -Werror, [
+AX_CHECK_COMPILER_FLAGS([-Watomic-properties -Werror], [
 	OBJCFLAGS="$OBJCFLAGS -Watomic-properties"
 	TESTS_OBJCFLAGS="$TESTS_OBJCFLAGS -Wno-atomic-properties"
 ])
 
 AC_MSG_CHECKING(whether Objective C compiler supports properties)