diff --git a/java.source/src/org/netbeans/api/java/source/ModificationResult.java b/java.source/src/org/netbeans/api/java/source/ModificationResult.java
--- a/java.source/src/org/netbeans/api/java/source/ModificationResult.java
+++ b/java.source/src/org/netbeans/api/java/source/ModificationResult.java
@@ -619,6 +619,9 @@
             
             do {
                 read = delegate.read(cbuf, off, len);
+                if (read == -1) {
+                    return -1;
+                }
                 j = 0;
 
                 for (int i = off; i < off + read; i++) {