diff --git src/3rdparty/harfbuzz/src/harfbuzz-shaper.cpp src/3rdparty/harfbuzz/src/harfbuzz-shaper.cpp
index 76c5177..0a564c1 100644
--- src/3rdparty/harfbuzz/src/harfbuzz-shaper.cpp
+++ src/3rdparty/harfbuzz/src/harfbuzz-shaper.cpp
@@ -464,6 +464,15 @@ void HB_HeuristicSetGlyphAttributes(HB_ShaperItem *item)
     // ### zeroWidth and justification are missing here!!!!!
 
     assert(item->num_glyphs <= length);
+    // RJVB: runtime assert and account for situations that can occur with newer HB versions
+    if (static_cast<hb_int32>(length) <= 0 || item->num_glyphs > length) {
+        return;
+    }
+//     if (length > item->num_glyphs) {
+//         fprintf(stderr, "QScriptEngine::heuristicSetGlyphAttributes, setting length=%u to num_glyphs=%d\n",
+//             length, item->num_glyphs);
+//         length = item->num_glyphs;
+//     }
 
 //     qDebug("QScriptEngine::heuristicSetGlyphAttributes, num_glyphs=%d", item->num_glyphs);
     HB_GlyphAttributes *attributes = item->attributes;
@@ -562,10 +571,12 @@ void HB_HeuristicSetGlyphAttributes(HB_ShaperItem *item)
         lastCat = cat;
     }
     pos = logClusters[length-1];
-    if (lastCat == HB_Separator_Space)
-        attributes[pos].justification = HB_Space;
-    else
-        attributes[pos].justification = HB_Character;
+    if (attributes && pos>= 0 && pos < item->num_glyphs) {
+        if (lastCat == HB_Separator_Space)
+            attributes[pos].justification = HB_Space;
+        else
+            attributes[pos].justification = HB_Character;
+    }
 }
 
 #ifndef NO_OPENTYPE