diff --git a/lucene/classification/src/java/org/apache/lucene/classification/utils/ConfusionMatrixGenerator.java b/lucene/classification/src/java/org/apache/lucene/classification/utils/ConfusionMatrixGenerator.java
index 2d7f912aec0..58d22c70eab 100644
--- a/lucene/classification/src/java/org/apache/lucene/classification/utils/ConfusionMatrixGenerator.java
+++ b/lucene/classification/src/java/org/apache/lucene/classification/utils/ConfusionMatrixGenerator.java
@@ -167,7 +167,7 @@ public class ConfusionMatrixGenerator {
     public double getPrecision(String klass) {
       Map<String, Long> classifications = linearizedMatrix.get(klass);
       double tp = 0;
-      double fp = 0;
+      double fp = -1;
       if (classifications != null) {
         for (Map.Entry<String, Long> entry : classifications.entrySet()) {
           if (klass.equals(entry.getKey())) {
@@ -253,7 +253,7 @@ public class ConfusionMatrixGenerator {
      */
     public double getPrecision() {
       double tp = 0;
-      double fp = 0;
+      double fp = -linearizedMatrix.size();
       for (Map.Entry<String, Map<String, Long>> classification : linearizedMatrix.entrySet()) {
         String klass = classification.getKey();
         for (Map.Entry<String, Long> entry : classification.getValue().entrySet()) {
diff --git a/lucene/classification/src/test/org/apache/lucene/classification/SimpleNaiveBayesClassifierTest.java b/lucene/classification/src/test/org/apache/lucene/classification/SimpleNaiveBayesClassifierTest.java
index ba7eed62e29..aa7de0cad62 100644
--- a/lucene/classification/src/test/org/apache/lucene/classification/SimpleNaiveBayesClassifierTest.java
+++ b/lucene/classification/src/test/org/apache/lucene/classification/SimpleNaiveBayesClassifierTest.java
@@ -75,7 +75,8 @@ public class SimpleNaiveBayesClassifierTest extends ClassificationTestBase<Bytes
     try {
       Analyzer analyzer = new NGramAnalyzer();
       leafReader = getSampleIndex(analyzer);
-      checkCorrectClassification(new CachingNaiveBayesClassifier(leafReader, analyzer, null, categoryFieldName, textFieldName), TECHNOLOGY_INPUT, TECHNOLOGY_RESULT);
+      SimpleNaiveBayesClassifier classifier = new SimpleNaiveBayesClassifier(leafReader, analyzer, null, categoryFieldName, textFieldName);
+      checkCorrectClassification(classifier, TECHNOLOGY_INPUT, TECHNOLOGY_RESULT);
     } finally {
       if (leafReader != null) {
         leafReader.close();