diff --git a/projects/core/src/main/java/dan200/computercraft/core/filesystem/MemoryMount.java b/projects/core/src/main/java/dan200/computercraft/core/filesystem/MemoryMount.java
index c8e09a586..2db0154b6 100644
--- a/projects/core/src/main/java/dan200/computercraft/core/filesystem/MemoryMount.java
+++ b/projects/core/src/main/java/dan200/computercraft/core/filesystem/MemoryMount.java
@@ -275,9 +275,9 @@ public final class MemoryMount extends AbstractInMemoryMount<MemoryMount.FileEnt
             checkClosed();
 
             var backing = Nullability.assertNonNull(entry.contents);
-            if (position >= backing.length) return -1;
+            if (position >= entry.length) return -1;
 
-            var remaining = Math.min(backing.length - (int) position, destination.remaining());
+            var remaining = Math.min(entry.length - (int) position, destination.remaining());
             destination.put(backing, (int) position, remaining);
             position += remaining;
             return remaining;
@@ -285,7 +285,7 @@ public final class MemoryMount extends AbstractInMemoryMount<MemoryMount.FileEnt
 
         private byte[] ensureCapacity(int capacity) {
             var contents = Nullability.assertNonNull(entry.contents);
-            if (capacity >= entry.length) {
+            if (capacity >= contents.length) {
                 var newCapacity = Math.max(capacity, contents.length << 1);
                 contents = entry.contents = Arrays.copyOf(contents, newCapacity);
             }