diff --git a/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java b/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java
index 178f6568ee..65c95ffee0 100644
--- a/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java
+++ b/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java
@@ -36,6 +36,7 @@ import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
+import org.apache.commons.math3.util.ArithmeticUtils;
 import org.apache.poi.EmptyFileException;
 import org.apache.poi.poifs.common.POIFSBigBlockSize;
 import org.apache.poi.poifs.common.POIFSConstants;
@@ -407,7 +408,8 @@ public class POIFSFileSystem extends BlockStore
         newBAT.setOurBlockIndex(offset);
         // Ensure there's a spot in the file for it
         ByteBuffer buffer = ByteBuffer.allocate(bigBlockSize.getBigBlockSize());
-        int writeTo = (1 + offset) * bigBlockSize.getBigBlockSize(); // Header isn't in BATs
+        // Header isn't in BATs
+        long writeTo = ArithmeticUtils.mulAndCheck((1 + (long)offset), (long)bigBlockSize.getBigBlockSize());
         _data.write(buffer, writeTo);
         // All done
         return newBAT;
diff --git a/src/java/org/apache/poi/poifs/filesystem/TempFilePOIFSFileSystem.java b/src/java/org/apache/poi/poifs/filesystem/TempFilePOIFSFileSystem.java
index c16ff035a0..be162b6079 100644
--- a/src/java/org/apache/poi/poifs/filesystem/TempFilePOIFSFileSystem.java
+++ b/src/java/org/apache/poi/poifs/filesystem/TempFilePOIFSFileSystem.java
@@ -42,7 +42,7 @@ public class TempFilePOIFSFileSystem extends POIFSFileSystem {
     }
 
     public void close() throws IOException {
-        if (tempFile != null) tempFile.delete();
+        if (tempFile != null && tempFile.exists()) tempFile.delete();
         super.close();
     }