diff --git a/cache/src/main/kotlin/org/openrs2/cache/Js5Compression.kt b/cache/src/main/kotlin/org/openrs2/cache/Js5Compression.kt
index d07eb3f9fd..ff09f51d39 100644
--- a/cache/src/main/kotlin/org/openrs2/cache/Js5Compression.kt
+++ b/cache/src/main/kotlin/org/openrs2/cache/Js5Compression.kt
@@ -290,9 +290,7 @@ public object Js5Compression {
         // Run the entire decompression algorithm to confirm the key is valid.
         decrypt(input, lenWithUncompressedLen, key).use { plaintext ->
             val uncompressedLen = plaintext.readInt()
-            if (uncompressedLen < 0) {
-                throw AssertionError()
-            }
+            check(uncompressedLen >= 0)
 
             try {
                 OutputStream.nullOutputStream().use { output ->