diff --git a/src/opentype/GlyphIterator.js b/src/opentype/GlyphIterator.js
index b22ad30b..54b1468d 100644
--- a/src/opentype/GlyphIterator.js
+++ b/src/opentype/GlyphIterator.js
@@ -4,10 +4,11 @@ export default class GlyphIterator {
     this.reset(options);
   }
 
-  reset(options = {}, index = 0) {
+  reset(options = {}, index = 0, markFilteringSet = null) {
     this.options = options;
     this.flags = options.flags || {};
     this.markAttachmentType = options.markAttachmentType || 0;
+    this.markFilteringSet = markFilteringSet;
     this.index = index;
   }
 
@@ -16,6 +17,12 @@ export default class GlyphIterator {
   }
 
   shouldIgnore(glyph) {
+    // useMarkFilteringSet (lookup flag 0x10) overrides ignoreMarks and
+    // markAttachmentType for marks: a mark is considered only if it is in
+    // the filtering set, otherwise it is skipped.
+    if (this.flags.useMarkFilteringSet && glyph.isMark) {
+      return !this.markFilteringSet?.has(glyph.id);
+    }
     return (this.flags.ignoreMarks && glyph.isMark) ||
            (this.flags.ignoreBaseGlyphs && glyph.isBase) ||
            (this.flags.ignoreLigatures && glyph.isLigature) ||
diff --git a/src/opentype/OTProcessor.js b/src/opentype/OTProcessor.js
index 80d1ce69..2a57a2d7 100644
--- a/src/opentype/OTProcessor.js
+++ b/src/opentype/OTProcessor.js
@@ -191,7 +191,7 @@ export default class OTProcessor {
 
     for (let { feature, lookup } of lookups) {
       this.currentFeature = feature;
-      this.glyphIterator.reset(lookup.flags);
+      this.glyphIterator.reset(lookup.flags, 0, this.getMarkFilteringSet(lookup));
 
       while (this.glyphIterator.index < glyphs.length) {
         if (!(feature in this.glyphIterator.cur.features)) {
@@ -217,16 +217,17 @@ export default class OTProcessor {
 
   applyLookupList(lookupRecords) {
     let options = this.glyphIterator.options;
+    let markFilteringSet = this.glyphIterator.markFilteringSet;
     let glyphIndex = this.glyphIterator.index;
 
     for (let lookupRecord of lookupRecords) {
       // Reset flags and find glyph index for this lookup record
-      this.glyphIterator.reset(options, glyphIndex);
+      this.glyphIterator.reset(options, glyphIndex, markFilteringSet);
       this.glyphIterator.increment(lookupRecord.sequenceIndex);
 
       // Get the lookup and setup flags for subtables
       let lookup = this.table.lookupList.get(lookupRecord.lookupListIndex);
-      this.glyphIterator.reset(lookup.flags, this.glyphIterator.index);
+      this.glyphIterator.reset(lookup.flags, this.glyphIterator.index, this.getMarkFilteringSet(lookup));
 
       // Apply lookup subtables until one matches
       for (let table of lookup.subTables) {
@@ -236,10 +237,34 @@ export default class OTProcessor {
       }
     }
 
-    this.glyphIterator.reset(options, glyphIndex);
+    this.glyphIterator.reset(options, glyphIndex, markFilteringSet);
     return true;
   }
 
+  getMarkFilteringSet(lookup) {
+    if (!lookup.flags.flags.useMarkFilteringSet) {
+      return null;
+    }
+    let coverage = this.font.GDEF?.markGlyphSetsDef?.coverage?.[lookup.markFilteringSet];
+    if (!coverage) {
+      return null;
+    }
+    let cache = (this._coverageSetCache ??= new Map());
+    let set = cache.get(coverage);
+    if (!set) {
+      set = new Set();
+      if (coverage.glyphs) {
+        for (let id of coverage.glyphs) set.add(id);
+      } else if (coverage.rangeRecords) {
+        for (let { start, end } of coverage.rangeRecords) {
+          for (let id = start; id <= end; id++) set.add(id);
+        }
+      }
+      cache.set(coverage, set);
+    }
+    return set;
+  }
+
   coverageIndex(coverage, glyph) {
     if (glyph == null) {
       glyph = this.glyphIterator.cur.id;
diff --git a/test/shaping.js b/test/shaping.js
index dc005ea0..337b4b29 100644
--- a/test/shaping.js
+++ b/test/shaping.js
@@ -56,6 +56,18 @@ describe('shaping', function () {
       '218+545|11+1781|94+1362|26@35,0+1139|34+564|32+1250|3+532|9+1904|96+1088|93+1383|51+569|8+1904|' +
       '3+532|33+1225|21+1470|3+532|96+1088|17+1496|96+1088|17+1496|32+1250|3+532|9+1904|95+1104|12+1781|39+1052');
 
+    // Exercises the useMarkFilteringSet lookup flag: Mada's `rclt` chain
+    // rule fires for [Jeem-form, ar1Dot.below, kasra] and substitutes the
+    // kasra with a positioned variant (`uni0650.alt`). The lookup carries
+    // a mark filtering set containing only the below-marks, so when an
+    // above-mark (fatha) sits between the dot and the kasra the iterator
+    // must skip it. Without the flag honoured, fontkit sees the fatha as
+    // the immediate predecessor of the kasra, the backtrack fails to
+    // match and the kasra is left unsubstituted.
+    test('should honour useMarkFilteringSet during contextual matching',
+      'Mada/Mada-VF.ttf', 'جَِ',
+      '86@873,-335+0|83@253,495+0|111@273,-95+0|8+568');
+
     test('should shape N\'Ko text', 'NotoSans/NotoSansNKo-Regular.ttf', 'ߞߊ߬ ߞߐߕߐ߮ ߞߎߘߊ ߘߏ߫ ߘߊߦߟߍ߬ ߸ ߏ߬',
       '52@10,-300+0|23+1128|3+532|64+985|3+532|52@150,-300+0|84+1268|139+1184|160+1067|76+543|119+1622|3+532|51@10,-300+0|90+1128' +
       '|119+1622|3+532|75+543|118+1622|88+1212|137+1114|3+532|54@170,0+0|93+1321|109+1155|94+1321|137+1114|3+532|52@-210,0+0|75+543|137+1114');