diff --git a/xs.h b/xs.h
index 2fc7dda..fef91b7 100644
--- a/xs.h
+++ b/xs.h
@@ -1057,12 +1057,12 @@ xs_data *xs_data_new(const void *data, int size)
     xs_data *v;
 
     /* add the overhead (data type + 24bit size) */
-    size += 4;
+    int total_size = size + 4;
 
-    v = xs_realloc(NULL, _xs_blk_size(size));
+    v = xs_realloc(NULL, _xs_blk_size(total_size));
     v[0] = XSTYPE_DATA;
 
-    _xs_put_24b(v + 1, size);
+    _xs_put_24b(v + 1, total_size);
 
     memcpy(&v[4], data, size);
 
diff --git a/xs_curl.h b/xs_curl.h
index e880a0d..ca90f92 100644
--- a/xs_curl.h
+++ b/xs_curl.h
@@ -55,7 +55,7 @@ static int _data_callback(void *buffer, size_t size,
 
     /* open space */
     pd->size += sz;
-    pd->data = xs_realloc(pd->data, pd->size + 1);
+    pd->data = xs_realloc(pd->data, _xs_blk_size(pd->size + 1));
 
     /* copy data */
     memcpy(pd->data + pd->offset, buffer, sz);