diff --git a/fixtures/jsii-calc/lib/decorators.ts b/fixtures/jsii-calc/lib/decorators.ts
new file mode 100644
index 00000000..a3e89780
--- /dev/null
+++ b/fixtures/jsii-calc/lib/decorators.ts
@@ -0,0 +1,50 @@
+type Constructor = { new (...args: any[]): {} };
+
+export function functionReturnsClasstype<T extends Constructor>(ctr: T) {
+  return class extends ctr {
+  };
+}
+
+/**
+ * A class decorator that changes inherited state and adds a readonly field to the class.
+ *
+ * This wasn't the thing that was exploding, see `function-returning-anonymous-class.ts` for that.
+ * Nevertheless, this makes for a good class decorator demo.
+ */
+export function classDecorator(x: typeof SomeDecoratedClass): typeof SomeDecoratedClass {
+  const ret = class extends x {
+    constructor() {
+      super();
+      this.state = this.state + this.state;
+    }
+  };
+
+  // This adds a field to the class, but we can't reflect that in the type because of the limitations
+  // of decorators. That's we advertise it through interface merging below.
+  (ret.prototype as any)['field'] = 'some_added_field';
+
+  return ret;
+}
+
+@classDecorator
+export class SomeDecoratedClass {
+  protected state = 'state';
+
+  public accessState() {
+    return this.state;
+  }
+}
+
+export interface SomeDecoratedClass {
+  readonly field: string;
+}
+
+/**
+ * Exercise the above code
+ */
+function tryDecoratedClass() {
+  const instance = new SomeDecoratedClass();
+  return instance.field;
+}
+// Suppress unused locals warnings
+void tryDecoratedClass;
\ No newline at end of file
diff --git a/fixtures/jsii-calc/lib/function-returning-anonymous-class.ts b/fixtures/jsii-calc/lib/function-returning-anonymous-class.ts
new file mode 100644
index 00000000..4e0efe37
--- /dev/null
+++ b/fixtures/jsii-calc/lib/function-returning-anonymous-class.ts
@@ -0,0 +1,17 @@
+type Constructor = { new (...args: any[]): {} };
+
+/**
+ * Just the mere presence of this function is enough to break jsii, even if it's not exported from
+ * the jsii root module.
+ *
+ * The reason is that when we add deprecation warnings we visit all functions in all files.
+ */
+export function propertyInjectionDecorator<T extends Constructor>(ctr: T) {
+  // Important for the bug: the anonymous class extends something, *and*
+  // declares a method.
+  return class extends ctr {
+    public someMethod(): string {
+      return 'abc';
+    }
+  };
+}
\ No newline at end of file
diff --git a/fixtures/jsii-calc/lib/index.ts b/fixtures/jsii-calc/lib/index.ts
index 49fec18b..b0b2f91a 100644
--- a/fixtures/jsii-calc/lib/index.ts
+++ b/fixtures/jsii-calc/lib/index.ts
@@ -9,6 +9,7 @@ export * from './stability';
 export * from './submodules';
 export * from './container-types';
 export * from './indirect-implementation';
+export * from './decorators';
 
 export * as submodule from './submodule';
 export * as onlystatic from './only-static';
diff --git a/src/common/symbol-id.ts b/src/common/symbol-id.ts
index 90209739..33333e44 100644
--- a/src/common/symbol-id.ts
+++ b/src/common/symbol-id.ts
@@ -49,9 +49,13 @@ interface SymbolIdOptions {
  */
 export function symbolIdentifier(
   typeChecker: ts.TypeChecker,
-  sym: ts.Symbol,
+  sym: ts.Symbol | undefined,
   options: SymbolIdOptions = {},
 ): string | undefined {
+  if (!sym) {
+    return undefined;
+  }
+
   // If this symbol happens to be an alias, resolve it first
   // eslint-disable-next-line no-bitwise
   while ((sym.flags & ts.SymbolFlags.Alias) !== 0) {
diff --git a/test/__snapshots__/integration.test.ts.snap b/test/__snapshots__/integration.test.ts.snap
index 87be9bde..ab2a5783 100644
--- a/test/__snapshots__/integration.test.ts.snap
+++ b/test/__snapshots__/integration.test.ts.snap
@@ -1693,14 +1693,14 @@ const foo = 'bar';
     "jsii-calc.anonymous": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 28,
+        "line": 29,
       },
       "symbolId": "lib/anonymous/index:",
     },
     "jsii-calc.cdk16625": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 24,
+        "line": 25,
       },
       "symbolId": "lib/cdk16625/index:",
     },
@@ -1714,7 +1714,7 @@ const foo = 'bar';
     "jsii-calc.cdk22369": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 25,
+        "line": 26,
       },
       "symbolId": "lib/cdk22369/index:",
     },
@@ -1728,7 +1728,7 @@ const foo = 'bar';
     "jsii-calc.homonymousForwardReferences": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 30,
+        "line": 31,
       },
       "readme": {
         "markdown": "Verifies homonymous forward references don't trip the Python type checker
@@ -1756,35 +1756,35 @@ information, which was reported in https://github.com/aws/jsii/issues/3818.
     "jsii-calc.jsii3656": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 26,
+        "line": 27,
       },
       "symbolId": "lib/jsii3656/index:",
     },
     "jsii-calc.module2530": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 21,
+        "line": 22,
       },
       "symbolId": "lib/module2530/index:",
     },
     "jsii-calc.module2617": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 17,
+        "line": 18,
       },
       "symbolId": "lib/module2617/index:",
     },
     "jsii-calc.module2647": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 16,
+        "line": 17,
       },
       "symbolId": "lib/module2647/index:",
     },
     "jsii-calc.module2689": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 18,
+        "line": 19,
       },
       "symbolId": "lib/module2689/index:",
     },
@@ -1819,7 +1819,7 @@ information, which was reported in https://github.com/aws/jsii/issues/3818.
     "jsii-calc.module2692": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 20,
+        "line": 21,
       },
       "symbolId": "lib/module2692/index:",
     },
@@ -1840,21 +1840,21 @@ information, which was reported in https://github.com/aws/jsii/issues/3818.
     "jsii-calc.module2700": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 22,
+        "line": 23,
       },
       "symbolId": "lib/module2700/index:",
     },
     "jsii-calc.module2702": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 19,
+        "line": 20,
       },
       "symbolId": "lib/module2702/index:",
     },
     "jsii-calc.nodirect": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 15,
+        "line": 16,
       },
       "symbolId": "lib/no-direct-types/index:",
     },
@@ -1875,14 +1875,14 @@ information, which was reported in https://github.com/aws/jsii/issues/3818.
     "jsii-calc.onlystatic": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 14,
+        "line": 15,
       },
       "symbolId": "lib/only-static/index:",
     },
     "jsii-calc.submodule": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 13,
+        "line": 14,
       },
       "readme": {
         "markdown": "Read you, read me
@@ -1952,7 +1952,7 @@ This is the readme of the \`jsii-calc.submodule.isolated\` module.
     "jsii-calc.union": {
       "locationInModule": {
         "filename": "lib/index.ts",
-        "line": 29,
+        "line": 30,
       },
       "symbolId": "lib/union:",
     },
@@ -14613,6 +14613,72 @@ this it would break runtime type checks in the JVM or CLR.",
       ],
       "symbolId": "lib/calculator:SmellyStruct",
     },
+    "jsii-calc.SomeDecoratedClass": {
+      "assembly": "jsii-calc",
+      "docs": {
+        "stability": "stable",
+      },
+      "fqn": "jsii-calc.SomeDecoratedClass",
+      "initializer": {
+        "docs": {
+          "stability": "stable",
+        },
+      },
+      "kind": "class",
+      "locationInModule": {
+        "filename": "lib/decorators.ts",
+        "line": 29,
+      },
+      "methods": [
+        {
+          "docs": {
+            "stability": "stable",
+          },
+          "locationInModule": {
+            "filename": "lib/decorators.ts",
+            "line": 33,
+          },
+          "name": "accessState",
+          "returns": {
+            "type": {
+              "primitive": "string",
+            },
+          },
+        },
+      ],
+      "name": "SomeDecoratedClass",
+      "properties": [
+        {
+          "docs": {
+            "stability": "stable",
+          },
+          "immutable": true,
+          "locationInModule": {
+            "filename": "lib/decorators.ts",
+            "line": 39,
+          },
+          "name": "field",
+          "type": {
+            "primitive": "string",
+          },
+        },
+        {
+          "docs": {
+            "stability": "stable",
+          },
+          "locationInModule": {
+            "filename": "lib/decorators.ts",
+            "line": 31,
+          },
+          "name": "state",
+          "protected": true,
+          "type": {
+            "primitive": "string",
+          },
+        },
+      ],
+      "symbolId": "lib/decorators:SomeDecoratedClass",
+    },
     "jsii-calc.SomeTypeJsii976": {
       "assembly": "jsii-calc",
       "docs": {