diff --git a/src/java/org/apache/lucene/index/SegmentReader.java b/src/java/org/apache/lucene/index/SegmentReader.java
index 9e6ba66cbf3..7d69a05fc17 100644
--- a/src/java/org/apache/lucene/index/SegmentReader.java
+++ b/src/java/org/apache/lucene/index/SegmentReader.java
@@ -100,7 +100,7 @@ class SegmentReader extends IndexReader {
                            SegmentReader.class.getName());
       IMPL = Class.forName(name);
     } catch (ClassNotFoundException e) {
-      throw new RuntimeException(e);
+      throw new RuntimeException("cannot load SegmentReader class: " + e.getMessage());
     }
   }
 
@@ -123,7 +123,7 @@ class SegmentReader extends IndexReader {
     try {
       instance = (SegmentReader)IMPL.newInstance();
     } catch (Exception e) {
-      throw new RuntimeException(e);
+      throw new RuntimeException("cannot load SegmentReader class: " + e.getMessage());
     }
     instance.init(dir, sis, closeDir, ownDir);
     instance.initialize(si);
diff --git a/src/java/org/apache/lucene/store/FSDirectory.java b/src/java/org/apache/lucene/store/FSDirectory.java
index 82e3ed5ed6a..f82ecc28ea9 100644
--- a/src/java/org/apache/lucene/store/FSDirectory.java
+++ b/src/java/org/apache/lucene/store/FSDirectory.java
@@ -65,7 +65,7 @@ public class FSDirectory extends Directory {
                            FSDirectory.class.getName());
       IMPL = Class.forName(name);
     } catch (ClassNotFoundException e) {
-      throw new RuntimeException(e);
+      throw new RuntimeException("cannot load FSDirectory class: " + e.getMessage());
     }
   }
 
@@ -115,7 +115,7 @@ public class FSDirectory extends Directory {
         try {
           dir = (FSDirectory)IMPL.newInstance();
         } catch (Exception e) {
-          throw new RuntimeException(e);
+          throw new RuntimeException("cannot load FSDirectory class: " + e.getMessage());
         }
         dir.init(file, create);
         DIRECTORIES.put(file, dir);