diff --git a/configure.ac b/configure.ac
index 71593bdf..b250ac3b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -154,6 +154,7 @@ dnl   AX_CHECK_COMPILE_FLAG([-fno-strict-overflow], [CPPFLAGS="$CPPFLAGS -fno-st
    AX_CHECK_COMPILE_FLAG([-Wno-format-nonliteral], [CFLAGS="$CFLAGS -Wno-format-nonliteral"])
    AX_CHECK_COMPILE_FLAG([-Werror=conditional-uninitialized], [CFLAGS="$CFLAGS -Werror=conditional-uninitialized"])
    AX_CHECK_COMPILE_FLAG([-Werror=uninitialized], [CFLAGS="$CFLAGS -Werror=uninitialized"])
+   AX_CHECK_COMPILE_FLAG([-Werror=unused-variable], [CFLAGS="$CFLAGS -Werror=unused-variable"])
    AX_CHECK_COMPILE_FLAG([-Werror=missing-field-initializers], [CFLAGS="$CFLAGS -Werror=missing-field-initializers"])
    AX_CHECK_COMPILE_FLAG([-Werror=missing-variable-declarations], [CFLAGS="$CFLAGS -Werror=missing-variable-declarations"])
    AX_CHECK_COMPILE_FLAG([-Werror=missing-prototypes], [CFLAGS="$CFLAGS -Werror=missing-prototypes"])