diff --git a/src/browser/parser/Parser.zig b/src/browser/parser/Parser.zig
index e313a3dba..d1c87e9b5 100644
--- a/src/browser/parser/Parser.zig
+++ b/src/browser/parser/Parser.zig
@@ -728,6 +728,7 @@ fn _appendCallback(self: *Parser, parent: *Node, node_or_text: h5e.NodeOrText) !
             try self.frame.appendNew(parent, child);
         },
         .text => |txt| try self.appendTextChunk(parent, txt),
+        .failed => {},
     }
 }
 
@@ -801,6 +802,7 @@ fn _appendBeforeSiblingCallback(self: *Parser, sibling: *Node, node_or_text: h5e
             break :blk child;
         },
         .text => |txt| try Frame.node_factory.createTextNode(self.frame, txt),
+        .failed => return,
     };
     try self.frame.insertNodeRelative(parent, node, .{ .before = sibling }, .{});
 }
diff --git a/src/browser/parser/html5ever.zig b/src/browser/parser/html5ever.zig
index 4d1a29776..4ccbe73b0 100644
--- a/src/browser/parser/html5ever.zig
+++ b/src/browser/parser/html5ever.zig
@@ -184,12 +184,15 @@ pub const AttributeIterator = extern struct {
 
 pub const NodeOrText = extern struct {
     tag: u8,
-    node: *anyopaque,
+    // Null for text. Also null for a node when its create callback failed:
+    // html5ever still appends the null ref it got back.
+    node: ?*anyopaque,
     text: StringSlice,
 
     pub fn toUnion(self: NodeOrText) Union {
         if (self.tag == 0) {
-            return .{ .node = @ptrCast(@alignCast(self.node)) };
+            const node = self.node orelse return .failed;
+            return .{ .node = @ptrCast(@alignCast(node)) };
         }
         return .{ .text = self.text.slice() };
     }
@@ -197,6 +200,8 @@ pub const NodeOrText = extern struct {
     const Union = union(enum) {
         node: *ParsedNode,
         text: []const u8,
+        // The create callback failed and already set Parser.err.
+        failed,
     };
 };
 
diff --git a/src/browser/tests/domparser.html b/src/browser/tests/domparser.html
index ec1b4c29a..4f328b625 100644
--- a/src/browser/tests/domparser.html
+++ b/src/browser/tests/domparser.html
@@ -506,6 +506,8 @@
     '<a b="1" b="2"/>',          // duplicate attribute
     '<x:a>1</x:a>',              // undeclared prefix
     '<a>&#0;</a>',
+    '<a><?1x?></a>',             // invalid processing instruction target
+    '<?1x?><a/>',
   ]) {
     testing.expectEqual(bad + ' -> error', bad + (isError(p.parseFromString(bad, 'text/xml')) ? ' -> error' : ' -> ok'));
   }