diff --git a/RELEASES.md b/RELEASES.md
index 1fa20bc5..ab80df3f 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -14,6 +14,17 @@ commits that introduce the changes.  To make a new release, run
 `tools/mkrelease`, which will handle updating the heading for you.
 
 
+NEXT
+====
+This is a bugfix release.
+
+Compiler
+--------
+- Input maps will now ensure that non-numeric string values result in `0`
+  rather than `NaN`, the latter of which results in undefined behavior in
+  the new classification system.
+
+
 v19.0.0 (2022-03-01)
 ====================
 This version includes a backwards-incomplatible change to enable the new
diff --git a/src/current/compiler/js.xsl b/src/current/compiler/js.xsl
index 65777141..1e2a9ade 100644
--- a/src/current/compiler/js.xsl
+++ b/src/current/compiler/js.xsl
@@ -2414,7 +2414,7 @@
         {
             // TODO: error
             if ( Array.isArray( input ) ) input = input[0];
-            return ( input === '' || input === undefined ) ? value : +input;
+            return ( input === '' || input === undefined ) ? value : +input||0;
         }
 
         // TODO: error for both
@@ -2428,9 +2428,9 @@
         return input.map( function( x ) {
             return ( depth === 2 )
               ? Array.isArray( x )
-                  ? x.map( function(s) { return +s; } )
+                  ? x.map( function(s) { return +s||0; } )
                   : [ x ]
-              : ( x === '' || x === undefined ) ? value : +x;
+              : ( x === '' || x === undefined ) ? value : +x||0;
         } );
     }
 
diff --git a/src/current/compiler/map.xsl b/src/current/compiler/map.xsl
index 15acbb74..9a6e5d58 100644
--- a/src/current/compiler/map.xsl
+++ b/src/current/compiler/map.xsl
@@ -796,7 +796,7 @@
               <call-template name="lvmc:gen-input-default">
                 <with-param name="sym" select="$sym" />
                 <with-param name="from-str">
-                  <text>''+val[i]</text>
+                  <text>+val[i]||0</text>
                 </with-param>
                 <!-- We have to reduce the nesting level by one because of
                      our outer loop, but we do not want to go below 0, which