diff --git a/src/viewer/hooks/useStructureRegularExpressionManager.ts b/src/viewer/hooks/useStructureRegularExpressionManager.ts
index 4d3eb56..9bba0e2 100644
--- a/src/viewer/hooks/useStructureRegularExpressionManager.ts
+++ b/src/viewer/hooks/useStructureRegularExpressionManager.ts
@@ -233,8 +233,10 @@ export const useStructureRegularExpressionSearch = (
 		const indexOfFirstObjectInMatch = logEntryCharIndexMaps.firstCharIndexMap.get(matchRanges[0]);
 		const indexOfLastObjectInMatch = logEntryCharIndexMaps.lastCharIndexMap.get(matchRanges[1]);
 
-		for (let i = indexOfFirstObjectInMatch; i <= indexOfLastObjectInMatch; i++) {
-			indexesOfEntriesInMatch.push(i);
+		if(indexOfFirstObjectInMatch && indexOfLastObjectInMatch) {
+			for (let i = indexOfFirstObjectInMatch; i <= indexOfLastObjectInMatch; i++) {
+				indexesOfEntriesInMatch.push(i);
+			}
 		}
 
 		resultingMatches.push(indexesOfEntriesInMatch);
diff --git a/src/viewer/types.d.ts b/src/viewer/types.d.ts
index 659c9d3..245709f 100644
--- a/src/viewer/types.d.ts
+++ b/src/viewer/types.d.ts
@@ -59,6 +59,6 @@ export interface Segment {
 }
 
 export interface LogEntryCharMaps {
-	firstCharIndexMap;
-	lastCharIndexMap;
+	firstCharIndexMap: Map<number, number>;
+	lastCharIndexMap: Map<number, number>;
 }