20_1_header_parsing.patch

diff --git a/src/js/storage.js b/src/js/storage.js
index 04bae91b..272127b0 100644
--- a/src/js/storage.js
+++ b/src/js/storage.js
@@ -764,15 +764,33 @@ self.addEventListener('hiddenSettingsChanged', ( ) => {
     }
     // Extract update frequency information
     const matches = head.match(/(?:^|\n)(?:!|# )[\t ]*Expires[\t ]*:[\t ]*(\d+)[\t ]*(h)?/i);
+    let v;
     if ( matches !== null ) {
-        let v = Math.max(parseInt(matches[1], 10), 1);
+        v = parseInt(matches[1], 10);
         if ( matches[2] !== undefined ) {
             v = Math.ceil(v / 24);
         }
-        if ( v !== listEntry.updateAfter ) {
-            this.assets.registerAssetSource(assetKey, { updateAfter: v });
+    }
+
+    if ( typeof v !== 'number' ) {
+        if ( typeof listEntry.nanoUpdateAfterDefault === 'number' ) {
+            v = listEntry.nanoUpdateAfterDefault;
+        } else {
+            // IMPORTANT! Must update this value if default update period is
+            // changed
+            v = 3;
         }
     }
+
+    if ( v < 1 ) {
+        v = 1;
+    } else if ( v > 60 ) {
+        v = 60;
+    }
+
+    if ( v !== listEntry.updateAfter ) {
+        this.assets.registerAssetSource(assetKey, { updateAfter: v });
+    }
 };
 
 /******************************************************************************/