diff --git a/packages/blaze/materializer.js b/packages/blaze/materializer.js
index 40e1338db..0a05ea85a 100644
--- a/packages/blaze/materializer.js
+++ b/packages/blaze/materializer.js
@@ -93,7 +93,7 @@ var materializeDOMInner = function (htmljs, intoArray, parentView, workStack) {
   throw new Error("Unexpected object in htmljs: " + htmljs);
 };
 
-const isPromiseLike = x => typeof x?.then === 'function';
+const isPromiseLike = x => !!x && typeof x.then === 'function';
 
 function waitForAllAttributesAndContinue(attrs, fn) {
   const promises = [];
diff --git a/packages/spacebars/spacebars-runtime.js b/packages/spacebars/spacebars-runtime.js
index 8baabead1..9f7f958b2 100644
--- a/packages/spacebars/spacebars-runtime.js
+++ b/packages/spacebars/spacebars-runtime.js
@@ -175,7 +175,7 @@ Spacebars.call = function (value/*, args*/) {
   }
 };
 
-const isPromiseLike = x => typeof x?.then === 'function';
+const isPromiseLike = x => !!x && typeof x.then === 'function';
 
 // Call this as `Spacebars.kw({ ... })`.  The return value
 // is `instanceof Spacebars.kw`.