diff --git a/ch12_mining.adoc b/ch12_mining.adoc
index db47e7aa..9b8c9796 100644
--- a/ch12_mining.adoc
+++ b/ch12_mining.adoc
@@ -840,7 +840,7 @@ below the target. The target and difficulty are inversely related.
 ====
 
 ++++
-<p class="fix_tracking">
+<p class="fix_tracking3">
 Bitcoin's PoW is very similar to the challenge
 shown in <a data-type="xref" href="#sha256_example_generator_output2">#sha256_example_generator_output2</a>. The miner constructs a
 candidate block filled with transactions. Next, the miner calculates the