diff --git a/configure b/configure
index 4e0dc3fb09..2281892657 100755
--- a/configure
+++ b/configure
@@ -380,8 +380,6 @@ sdl2_config="${SDL2_CONFIG-${cross_prefix}sdl2-config}"
 # 2s-complement style results. (Both clang and gcc agree that it
 # provides these semantics.)
 QEMU_CFLAGS="-fno-strict-aliasing -fno-common -fwrapv"
-QEMU_CFLAGS="-Wundef -Wwrite-strings -Wmissing-prototypes $QEMU_CFLAGS"
-QEMU_CFLAGS="-Wstrict-prototypes -Wredundant-decls $QEMU_CFLAGS"
 QEMU_CFLAGS="-D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE $QEMU_CFLAGS"
 
 QEMU_LDFLAGS=
@@ -1168,6 +1166,11 @@ fi
 # just silently disable some features, so it's too error prone.
 
 warn_flags=
+add_to warn_flags -Wundef
+add_to warn_flags -Wwrite-strings
+add_to warn_flags -Wmissing-prototypes
+add_to warn_flags -Wstrict-prototypes
+add_to warn_flags -Wredundant-decls
 add_to warn_flags -Wold-style-declaration
 add_to warn_flags -Wold-style-definition
 add_to warn_flags -Wtype-limits