diff --git a/rhelp/org.eclipse.statet.rhelp.core/src/org/eclipse/statet/internal/rhelp/core/SerUtil.java b/rhelp/org.eclipse.statet.rhelp.core/src/org/eclipse/statet/internal/rhelp/core/SerUtil.java
index aebde9e..7d56952 100644
--- a/rhelp/org.eclipse.statet.rhelp.core/src/org/eclipse/statet/internal/rhelp/core/SerUtil.java
+++ b/rhelp/org.eclipse.statet.rhelp.core/src/org/eclipse/statet/internal/rhelp/core/SerUtil.java
@@ -320,7 +320,7 @@
 		final String docDir= in.readString();
 		final ImList<DocResource> manuals;
 		{	final int count= in.readInt();
-			final DocResource[] array= new org.eclipse.statet.rhelp.core.DocResource[count];
+			final DocResource[] array= new @NonNull DocResource[count];
 			for (int i= 0; i < count; i++) {
 				array[i]= readDocResource(in);
 			}
@@ -387,8 +387,8 @@
 	}
 	
 	private RHelpKeywordGroup loadKeywordGroup(final DataStream in) throws IOException {
-		final String label= in.readString();
-		final String description= in.readString();
+		final String label= in.readNonNullString();
+		final String description= in.readNonNullString();
 		final int count= in.readInt();
 		final RHelpKeyword[] keywords= new @NonNull RHelpKeyword[count];
 		for (int i= 0; i < count; i++) {
@@ -411,8 +411,8 @@
 	
 	private RHelpKeyword loadKeyword(final DataStream in)
 			throws IOException {
-		final String keyword= in.readString();
-		final String description= in.readString();
+		final String keyword= in.readNonNullString();
+		final String description= in.readNonNullString();
 		final int n= in.readInt();
 		final RHelpKeyword[] nestedKeywords= new @NonNull RHelpKeyword[n];
 		for (int i= 0; i < n; i++) {