diff --git a/configure.ac b/configure.ac
index 7391ea6..3bbaa61 100644
--- a/configure.ac
+++ b/configure.ac
@@ -34,7 +34,7 @@ AC_CHECK_HEADERS([attr/xattr.h])
 AC_CHECK_HEADERS([sys/extattr.h])
 AC_CHECK_FUNCS([fallocate])
 
-CXXFLAGS="$CXXFLAGS -Wall -fno-exceptions -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=3 -std=c++11"
+CXXFLAGS="-Wall -fno-exceptions -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=3 -std=c++11 $CXXFLAGS"
 
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 dnl For macOS