diff --git a/zip-0317.html b/zip-0317.html
index 1d6ef4d1..60651bab 100644
--- a/zip-0317.html
+++ b/zip-0317.html
@@ -285,7 +285,9 @@ Pull-Request: &lt;<a href="https://github.com/zcash/zips/pull/631">https://githu
                          and add the transaction to the set of candidate transactions.</li>
                         <li>Repeat while there is any candidate transaction that pays at least the conventional fee:
                             <ol type="a">
-                                <li>Pick one of those transactions at random with probability in direct proportion to its weight ratio, and remove it from the set of candidate transactions. Let
+                                <li>Pick one of those transactions at random with probability in direct proportion to its
+                                    <span class="math">\(weight\_ratio\)</span>
+                                , and remove it from the set of candidate transactions. Let
                                     <span class="math">\(B\)</span>
                                  be the block template with this transaction included.</li>
                                 <li>If
@@ -295,7 +297,9 @@ Pull-Request: &lt;<a href="https://github.com/zcash/zips/pull/631">https://githu
                         </li>
                         <li>Repeat while there is any candidate transaction:
                             <ol type="a">
-                                <li>Pick one of those transactions at random with probability in direct proportion to its weight ratio, and remove it from the set of candidate transactions. Let
+                                <li>Pick one of those transactions at random with probability in direct proportion to its
+                                    <span class="math">\(weight\_ratio\)</span>
+                                , and remove it from the set of candidate transactions. Let
                                     <span class="math">\(B\)</span>
                                  be the block template with this transaction included.</li>
                                 <li>If
@@ -330,6 +334,17 @@ Pull-Request: &lt;<a href="https://github.com/zcash/zips/pull/631">https://githu
                     <p>The rationale for choosing
                         <span class="math">\(weight\_ratio\_cap = 4\)</span>
                      is as a compromise between not allowing any prioritization of transactions relative to those that pay the conventional fee, and allowing arbitrary prioritization based on ability to pay.</p>
+                    <p>Calculating
+                        <span class="math">\(tx.\!weight\_ratio\)</span>
+                     in terms of
+                        <span class="math">\(\mathsf{max}(1,\, tx.\!fee)\)</span>
+                     rather than just
+                        <span class="math">\(tx.\!fee\)</span>
+                     avoids needing to define "with probability in direct proportion to its
+                        <span class="math">\(weight\_ratio\!\)</span>
+                    " for the case where all remaining candidate transactions would have
+                        <span class="math">\(weight\_ratio = 0\!\)</span>
+                    .</p>
                 </section>
                 <section id="incentive-compatibility-for-miners"><h4><span class="section-heading">Incentive compatibility for miners</span><span class="section-anchor"> <a rel="bookmark" href="#incentive-compatibility-for-miners"><img width="24" height="24" class="section-anchor" src="assets/images/section-anchor.png" alt=""></a></span></h4>
                     <p>Miners have an incentive to make this change because:</p>
diff --git a/zip-0317.rst b/zip-0317.rst
index 36363446..86f46569 100644
--- a/zip-0317.rst
+++ b/zip-0317.rst
@@ -283,18 +283,18 @@ from a set of transactions in a node's mempool:
    conventional fee:
 
    a. Pick one of those transactions at random with probability in direct
-      proportion to its weight ratio, and remove it from the set of candidate
-      transactions. Let :math:`B` be the block template with this transaction
-      included.
+      proportion to its :math:`weight\_ratio`, and remove it from the set of
+      candidate transactions. Let :math:`B` be the block template with this
+      transaction included.
    b. If :math:`B` would be within the block size limit and block sigop
       limit [#sigop-limit]_, add the transaction to the block template.
 
 3. Repeat while there is any candidate transaction:
 
    a. Pick one of those transactions at random with probability in direct
-      proportion to its weight ratio, and remove it from the set of candidate
-      transactions. Let :math:`B` be the block template with this transaction
-      included.
+      proportion to its :math:`weight\_ratio`, and remove it from the set of
+      candidate transactions. Let :math:`B` be the block template with this
+      transaction included.
    b. If :math:`B` would be within the block size limit and block sigop
       limit [#sigop-limit]_ and :math:`block\_unpaid\_actions(B) \leq block\_unpaid\_action\_limit\!`,
       add the transaction to the block template.
@@ -338,6 +338,11 @@ between not allowing any prioritization of transactions relative to those that
 pay the conventional fee, and allowing arbitrary prioritization based on ability
 to pay.
 
+Calculating :math:`tx.\!weight\_ratio` in terms of :math:`\mathsf{max}(1,\, tx.\!fee)`
+rather than just :math:`tx.\!fee` avoids needing to define "with probability in direct
+proportion to its :math:`weight\_ratio\!`" for the case where all remaining candidate
+transactions would have :math:`weight\_ratio = 0\!`.
+
 Incentive compatibility for miners
 ''''''''''''''''''''''''''''''''''