diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index 9709a5e96d95..90576e05fef9 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -1140,7 +1140,8 @@ export default class ExpressionParser extends LValParser {
           return this.finishNode(node, "PipelinePrimaryTopicReference");
         }
 
-        if (isIdentifierStart(this.input.codePointAt(this.state.end))) {
+        const nextCh = this.input.codePointAt(this.state.end);
+        if (isIdentifierStart(nextCh) || nextCh === charCodes.backslash) {
           const start = this.state.start;
           node = (this.parseMaybePrivateName(true): N.PrivateName);
           if (this.match(tt._in)) {
diff --git a/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/input.js b/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/input.js
new file mode 100644
index 000000000000..78069bae8a6d
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/input.js
@@ -0,0 +1,6 @@
+class Foo {
+  #\u{61} = 1;
+  test() {
+    #\u{61} in {};
+  }
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/options.json b/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/options.json
new file mode 100644
index 000000000000..4f1c66180f1e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "privateIn"]
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/output.json b/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/output.json
new file mode 100644
index 000000000000..1e1d2919424f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/output.json
@@ -0,0 +1,98 @@
+{
+  "type": "File",
+  "start":0,"end":62,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":62,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":62,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":62,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":26,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":14}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":21,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":9},"identifierName":"a"},
+                  "name": "a"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":24,"end":25,"loc":{"start":{"line":2,"column":12},"end":{"line":2,"column":13}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":29,"end":60,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":29,"end":33,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":36,"end":60,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":42,"end":56,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":18}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":42,"end":55,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":17}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":42,"end":49,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":11}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":43,"end":49,"loc":{"start":{"line":4,"column":5},"end":{"line":4,"column":11},"identifierName":"a"},
+                          "name": "a"
+                        }
+                      },
+                      "operator": "in",
+                      "right": {
+                        "type": "ObjectExpression",
+                        "start":53,"end":55,"loc":{"start":{"line":4,"column":15},"end":{"line":4,"column":17}},
+                        "properties": []
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file