diff --git a/src/java/org/apache/commons/math/ode/sampling/AbstractStepInterpolator.java b/src/java/org/apache/commons/math/ode/sampling/AbstractStepInterpolator.java
index 3cc31f349..e650b5cee 100644
--- a/src/java/org/apache/commons/math/ode/sampling/AbstractStepInterpolator.java
+++ b/src/java/org/apache/commons/math/ode/sampling/AbstractStepInterpolator.java
@@ -362,7 +362,7 @@ public abstract class AbstractStepInterpolator
 
   /** {@inheritDoc} */
   public abstract void readExternal(ObjectInput in)
-    throws IOException;
+    throws IOException, ClassNotFoundException;
 
   /** Save the base state of the instance.
    * This method performs step finalization if it has not been done
diff --git a/src/java/org/apache/commons/math/ode/sampling/NordsieckStepInterpolator.java b/src/java/org/apache/commons/math/ode/sampling/NordsieckStepInterpolator.java
index 85fa2eee1..b408a0bae 100644
--- a/src/java/org/apache/commons/math/ode/sampling/NordsieckStepInterpolator.java
+++ b/src/java/org/apache/commons/math/ode/sampling/NordsieckStepInterpolator.java
@@ -187,18 +187,64 @@ public class NordsieckStepInterpolator extends AbstractStepInterpolator {
     @Override
     public void writeExternal(final ObjectOutput out)
         throws IOException {
+
+        // save the state of the base class
         writeBaseExternal(out);
+
+        // save the local attributes
+        out.writeDouble(scalingH);
+        out.writeDouble(referenceTime);
+
+        final int n = (currentState == null) ? -1 : currentState.length;
+        if (scaled == null) {
+            out.writeBoolean(false);
+        } else {
+            out.writeBoolean(true);
+            for (int j = 0; j < n; ++j) {
+                out.writeDouble(scaled[j]);
+            }
+        }
+
+        if (nordsieck == null) {
+            out.writeBoolean(false);
+        } else {
+            out.writeBoolean(true);
+            out.writeObject(nordsieck);
+        }
+
     }
 
     /** {@inheritDoc} */
     @Override
     public void readExternal(final ObjectInput in)
-        throws IOException {
+        throws IOException, ClassNotFoundException {
 
         // read the base class 
         final double t = readBaseExternal(in);
 
-        if ((scaled != null) && (nordsieck != null)) {
+        // read the local attributes
+        scalingH      = in.readDouble();
+        referenceTime = in.readDouble();
+
+        final int n = (currentState == null) ? -1 : currentState.length;
+        final boolean hasScaled = in.readBoolean();
+        if (hasScaled) {
+            scaled = new double[n];
+            for (int j = 0; j < n; ++j) {
+                scaled[j] = in.readDouble();
+            }
+        } else {
+            scaled = null;
+        }
+
+        final boolean hasNordsieck = in.readBoolean();
+        if (hasNordsieck) {
+            nordsieck = (Array2DRowRealMatrix) in.readObject();
+        } else {
+            nordsieck = null;
+        }
+
+        if (hasScaled && hasNordsieck) {
             // we can now set the interpolated time and state
             setInterpolatedTime(t);
         }
diff --git a/src/test/org/apache/commons/math/ode/sampling/NordsieckStepInterpolatorTest.java b/src/test/org/apache/commons/math/ode/sampling/NordsieckStepInterpolatorTest.java
index f7f772a53..1e2db9858 100644
--- a/src/test/org/apache/commons/math/ode/sampling/NordsieckStepInterpolatorTest.java
+++ b/src/test/org/apache/commons/math/ode/sampling/NordsieckStepInterpolatorTest.java
@@ -62,8 +62,8 @@ public class NordsieckStepInterpolatorTest {
             oos.writeObject(handler);
         }
 
-        assertTrue(bos.size () >  16000);
-        assertTrue(bos.size () <  17000);
+        assertTrue(bos.size () >  20000);
+        assertTrue(bos.size () <  25000);
 
         ByteArrayInputStream  bis = new ByteArrayInputStream(bos.toByteArray());
         ObjectInputStream     ois = new ObjectInputStream(bis);