diff --git a/src/nxt_clang.h b/src/nxt_clang.h
index 94638346e..6803ffc8b 100644
--- a/src/nxt_clang.h
+++ b/src/nxt_clang.h
@@ -252,7 +252,7 @@ nxt_popcount(unsigned int x)
 
 
 #define nxt_length(s)                                                         \
-    (sizeof(s) - 1)
+    (nxt_nitems(s) - 1)
 
 
 #endif /* _NXT_CLANG_H_INCLUDED_ */