diff --git a/src/helpers/elm/QueryFilterParser.ts b/src/helpers/elm/QueryFilterParser.ts
index 067dcefd..306d0e68 100644
--- a/src/helpers/elm/QueryFilterParser.ts
+++ b/src/helpers/elm/QueryFilterParser.ts
@@ -720,6 +720,11 @@ export function interpretEqual(equal: ELMEqual, library: ELM): EqualsFilter | Un
     propRef = equal.operand[0] as ELMProperty;
   }
 
+  if (propRef == null) {
+    withError.message = `could not resolve property ref for Equal:${equal.localId}. first operand is a ${equal.operand[0].type}`;
+    return { type: 'unknown', withError };
+  }
+
   if (isOfTypeGracefulError(propRef)) {
     return { type: 'unknown', withError: propRef };
   }
diff --git a/src/types/errors/GracefulError.ts b/src/types/errors/GracefulError.ts
index 40f4460d..86c947b1 100644
--- a/src/types/errors/GracefulError.ts
+++ b/src/types/errors/GracefulError.ts
@@ -6,7 +6,7 @@ export interface GracefulError {
 }
 
 export const isOfTypeGracefulError = (tbd: any): tbd is GracefulError => {
-  if ((tbd as GracefulError).message) {
+  if ((tbd as GracefulError)?.message) {
     return true;
   }
   return false;