diff --git a/lib/contextify.js b/lib/contextify.js
index 5875979..5695e0e 100644
--- a/lib/contextify.js
+++ b/lib/contextify.js
@@ -529,7 +529,8 @@ Decontextify.value = (value, traps, deepTraps, flags, mock) => {
 				} else if (instanceOf(value, WeakMap))        { return Decontextify.instance(value, host.WeakMap, deepTraps, flags, 'WeakMap');
 				} else if (instanceOf(value, Set))            { return Decontextify.instance(value, host.Set, deepTraps, flags, 'Set');
 				} else if (instanceOf(value, WeakSet))        { return Decontextify.instance(value, host.WeakSet, deepTraps, flags, 'WeakSet');
-				} else if (Promise && instanceOf(value, Promise)) { return Decontextify.instance(value, host.Promise, deepTraps, flags, 'Promise');
+				} else if (typeof Promise === 'function' && instanceOf(value, Promise)) {
+					return Decontextify.instance(value, host.Promise, deepTraps, flags, 'Promise');
 				} else if (local.Reflect.getPrototypeOf(value) === null) {
 					return Decontextify.instance(value, null, deepTraps, flags);
 				} else {
@@ -907,7 +908,8 @@ Contextify.value = (value, traps, deepTraps, flags, mock) => {
 				} else if (instanceOf(value, host.WeakMap))        { return Contextify.instance(value, WeakMap, deepTraps, flags, 'WeakMap');
 				} else if (instanceOf(value, host.Set))            { return Contextify.instance(value, Set, deepTraps, flags, 'Set');
 				} else if (instanceOf(value, host.WeakSet))        { return Contextify.instance(value, WeakSet, deepTraps, flags, 'WeakSet');
-				} else if (instanceOf(value, host.Promise))        { return Contextify.instance(value, Promise, deepTraps, flags, 'Promise');
+				} else if (typeof Promise === 'function' && instanceOf(value, host.Promise)) {
+					return Contextify.instance(value, Promise, deepTraps, flags, 'Promise');
 				} else if (instanceOf(value, host.Buffer))         { return Contextify.instance(value, LocalBuffer, deepTraps, flags, 'Uint8Array');
 				} else if (host.Reflect.getPrototypeOf(value) === null) {
 					return Contextify.instance(value, null, deepTraps, flags);