diff --git a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/BracketInserterTest.java b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/BracketInserterTest.java
index 1bba6821a4d..54f11358671 100644
--- a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/BracketInserterTest.java
+++ b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/BracketInserterTest.java
@@ -376,6 +376,16 @@ public class BracketInserterTest extends TestCase {
 		assertSingleLinkedPosition(INCLUDE_OFFSET + 1);
 	}
 
+	public void testInsertClosingQuoteInIncludeAtDocumentEnd_Bug309099() throws Exception {
+		int startOffset = TU_CONTENTS.length();
+		setCaret(startOffset);
+		type("#include ");
+		type('"');
+		assertEquals(startOffset + 11, fDocument.getLength());
+		assertEquals("#include \"\"", fDocument.get(startOffset, 11));
+		assertSingleLinkedPosition(startOffset + 10);
+	}
+
 	public void testAngleBrackets_165837() throws Exception {
 		setCaret(BODY_OFFSET);
 		type("cout << \n\"aaa\" ");
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/editor/CEditor.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/editor/CEditor.java
index e3c05d5cc43..c2adf580ac6 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/editor/CEditor.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/editor/CEditor.java
@@ -715,7 +715,7 @@ public class CEditor extends TextEditor implements ISelectionChangedListener, IC
 		}
 
 		private boolean isInsideStringInPreprocessorDirective(ITypedRegion partition, IDocument document, int offset) throws BadLocationException {
-			if (ICPartitions.C_PREPROCESSOR.equals(partition.getType())) {
+			if (ICPartitions.C_PREPROCESSOR.equals(partition.getType()) && offset < document.getLength()) {
 				// use temporary document to test whether offset is inside non-default partition
 				String directive = document.get(partition.getOffset(), offset - partition.getOffset() + 1);
 				int hashIdx = directive.indexOf('#');