diff --git a/.changeset/honest-hounds-exist.md b/.changeset/honest-hounds-exist.md
new file mode 100644
index 0000000000..59219e98af
--- /dev/null
+++ b/.changeset/honest-hounds-exist.md
@@ -0,0 +1,5 @@
+---
+'@backstage/core-components': patch
+---
+
+Fixes a problem where the `LogViewer` was not able to handle very large logs
diff --git a/packages/core-components/src/components/LogViewer/AnsiProcessor.ts b/packages/core-components/src/components/LogViewer/AnsiProcessor.ts
index d0f835a70e..bcd5af7ced 100644
--- a/packages/core-components/src/components/LogViewer/AnsiProcessor.ts
+++ b/packages/core-components/src/components/LogViewer/AnsiProcessor.ts
@@ -117,7 +117,7 @@ export class AnsiProcessor {
       return this.lines;
     }
 
-    if (text.startsWith(this.text)) {
+    if (this.text && text.startsWith(this.text)) {
       const lastLineIndex = this.lines.length > 0 ? this.lines.length - 1 : 0;
       const lastLine = this.lines[lastLineIndex] ?? new AnsiLine();
       const lastChunk = lastLine.lastChunk();
@@ -130,7 +130,7 @@ export class AnsiProcessor {
       lastLine.replaceLastChunk(newLines[0]?.chunks);
 
       this.lines[lastLineIndex] = lastLine;
-      this.lines.push(...newLines.slice(1));
+      this.lines = this.lines.concat(newLines.slice(1));
     } else {
       this.lines = this.processLines(text);
     }