diff --git a/src/od.c b/src/od.c
index c68d40bac..5dd9d9f4d 100644
--- a/src/od.c
+++ b/src/od.c
@@ -1421,8 +1421,8 @@ dump (void)
   int err;
   size_t n_bytes_read;
 
-  block[0] = alloca (bytes_per_block);
-  block[1] = alloca (bytes_per_block);
+  block[0] = xnmalloc (2, bytes_per_block);
+  block[1] = block[0] + bytes_per_block;
 
   current_offset = n_bytes_to_skip;
 
@@ -1487,6 +1487,8 @@ dump (void)
   if (limit_bytes_to_format && current_offset >= end_offset)
     err |= check_and_close (0);
 
+  free (block[0]);
+
   return err;
 }