diff --git a/src/utils/parseAssertions.ts b/src/utils/parseAssertions.ts
index 7a54a172777..4a0f535477a 100644
--- a/src/utils/parseAssertions.ts
+++ b/src/utils/parseAssertions.ts
@@ -19,7 +19,7 @@ export function getAssertionsFromImportExpression(node: ImportExpression): Recor
 			const key = getPropertyKey(property);
 			if (
 				typeof key === 'string' &&
-				typeof ((property as Property).value as Literal)?.value === 'string'
+				typeof ((property as Property).value as Literal).value === 'string'
 			) {
 				return [key, ((property as Property).value as Literal).value] as [string, string];
 			}
@@ -34,9 +34,10 @@ export function getAssertionsFromImportExpression(node: ImportExpression): Recor
 
 const getPropertyKey = (
 	property: Property | SpreadElement | ImportAttribute
-): LiteralValue | undefined =>
-	((property as Property | ImportAttribute).key as Identifier).name ||
-	((property as Property | ImportAttribute).key as Literal).value;
+): LiteralValue | undefined => {
+	const key = (property as Property | ImportAttribute).key;
+	return key && ((key as Identifier).name || (key as Literal).value);
+};
 
 export function getAssertionsFromImportExportDeclaration(
 	assertions: ImportAttribute[] | undefined
diff --git a/test/form/samples/import-assertions/assertion-shapes/_config.js b/test/form/samples/import-assertions/assertion-shapes/_config.js
new file mode 100644
index 00000000000..3686c79e002
--- /dev/null
+++ b/test/form/samples/import-assertions/assertion-shapes/_config.js
@@ -0,0 +1,7 @@
+module.exports = {
+	description: 'handles special shapes of assertions',
+	expectedWarnings: 'UNRESOLVED_IMPORT',
+	options: {
+		external: () => true
+	}
+};
diff --git a/test/form/samples/import-assertions/assertion-shapes/_expected.js b/test/form/samples/import-assertions/assertion-shapes/_expected.js
new file mode 100644
index 00000000000..b5d8cbaa42d
--- /dev/null
+++ b/test/form/samples/import-assertions/assertion-shapes/_expected.js
@@ -0,0 +1,4 @@
+import('external-a', { assert: { type: 'json' } });
+import('external-b');
+import('external-c');
+import('external-d');
diff --git a/test/form/samples/import-assertions/assertion-shapes/main.js b/test/form/samples/import-assertions/assertion-shapes/main.js
new file mode 100644
index 00000000000..a82cad812bc
--- /dev/null
+++ b/test/form/samples/import-assertions/assertion-shapes/main.js
@@ -0,0 +1,4 @@
+import('external-a', { 'assert': { 'type': 'json', foo: 1, ...{} } });
+import('external-b', { assert: {} });
+import('external-c', { ...{} });
+import('external-d', {});