1 files changed, 1 insertions, 1 deletions

diff --git a/cstring/include/cstring.h b/cstring/include/cstring.h
index 3e693e1..c24cd35 100644
--- a/cstring/include/cstring.h
+++ b/cstring/include/cstring.h
@@ -75,7 +75,7 @@ static inline void cstring_copy(char* dst, const char* src, size_t count) {
   static inline void STRING##_append_cstr_len(                                \
       STRING* a, const char* b, const size_t b_length) {                      \
     ASSERT(a->length + b_length + 1 <= SIZE);                                 \
-    cstring_copy(a->str + a->length, b, SIZE - a->length);                    \
+    cstring_copy(a->str + a->length, b, b_length);                            \
     a->length += b_length;                                                    \
   }                                                                           \
                                                                               \