diff --git a/src/libply/ply-buffer.h b/src/libply/ply-buffer.h
index fc7f4a89..2140e44d 100644
--- a/src/libply/ply-buffer.h
+++ b/src/libply/ply-buffer.h
@@ -55,12 +55,18 @@ void ply_buffer_remove_bytes_at_end (ply_buffer_t *buffer,
 const char *ply_buffer_get_bytes (ply_buffer_t *buffer);
 size_t ply_buffer_get_capacity (ply_buffer_t *buffer);
 char *ply_buffer_steal_bytes (ply_buffer_t *buffer);
-#define ply_buffer_borrow_bytes(buffer, bytes, size, capacity)                    \
-        for (bool _ran = false; *bytes = (char *) ply_buffer_get_bytes (buffer),    \
-             *size = ply_buffer_get_size (buffer),                                \
-             *capacity = ply_buffer_get_capacity (buffer),                        \
-             !_ran;                                                               \
-             ply_buffer_set_bytes (buffer, *bytes, *size, *capacity), _ran = true)
+#define ply_buffer_borrow_bytes(buffer, bytes, size, capacity)                 \
+        for (bool _ran = false;                                                \
+             !_ran && (*bytes = (char *) ply_buffer_get_bytes (buffer),        \
+                       *size = ply_buffer_get_size (buffer),                   \
+                       *capacity = ply_buffer_get_capacity (buffer)),          \
+             !_ran;                                                            \
+             ply_buffer_set_bytes (buffer, *bytes, *size, *capacity),          \
+             _ran = true,                                                      \
+             *bytes = NULL,                                                    \
+             *size = 0,                                                        \
+             *capacity = 0)
+
 size_t ply_buffer_get_size (ply_buffer_t *buffer);
 void ply_buffer_clear (ply_buffer_t *buffer);
 #endif