diff --git a/src/Logic/Tags/And.ts b/src/Logic/Tags/And.ts
index b1b69b8ab..77ec8e5bb 100644
--- a/src/Logic/Tags/And.ts
+++ b/src/Logic/Tags/And.ts
@@ -314,6 +314,14 @@ export class And<T extends TagsFilter = TagsFilter> extends TagsFilter {
             for (let j = i + 1; j < optimized.length; j++) {
                 const ti = optimized[i]
                 const tj = optimized[j]
+                if (
+                    !ti ||
+                    !tj ||
+                    typeof ti.shadows !== "function" ||
+                    typeof tj.shadows !== "function"
+                ) {
+                    continue
+                }
                 if (ti.shadows(tj)) {
                     // if 'ti' is true, this implies 'tj' is always true as well.
                     // if 'ti' is false, then 'tj' might be true or false
@@ -322,6 +330,7 @@ export class And<T extends TagsFilter = TagsFilter> extends TagsFilter {
                     // If 'ti' is true, then 'tj' will be true too and 'tj' can be ignored
                     // If 'ti' is false, then the entire expression will be false and it doesn't matter what 'tj' yields
                     optimized.splice(j, 1)
+                    j--
                 } else if (tj.shadows(ti)) {
                     optimized.splice(i, 1)
                     i--