diff --git a/auto/cc/clang b/auto/cc/clang
index 2611caa65..0cca3442e 100644
--- a/auto/cc/clang
+++ b/auto/cc/clang
@@ -82,6 +82,7 @@ fi
 # warnings
 
 CFLAGS="$CFLAGS $NGX_CLANG_OPT -Wall -Wextra -Wpointer-arith"
+CFLAGS="$CFLAGS -Wconditional-uninitialized"
 #CFLAGS="$CFLAGS -Wmissing-prototypes"
 
 # we have a lot of unused function arguments