diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelAction.java
index abb6cfb06b1..4233110abfe 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelAction.java
@@ -10,6 +10,7 @@ import org.elasticsearch.action.ActionRequest;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionType;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.xpack.core.ml.inference.TrainedModelConfig;
@@ -137,6 +138,15 @@ public class InternalInferModelAction extends ActionType<InternalInferModelActio
             return Objects.hash(modelId, objectsToInfer, update, previouslyLicensed);
         }
 
+        @Override
+        public String toString() {
+            return "Request{" +
+                "modelId='" + modelId + '\'' +
+                ", objectsToInfer=" + objectsToInfer +
+                ", update=" + Strings.toString(update) +
+                ", previouslyLicensed=" + previouslyLicensed +
+                '}';
+        }
     }
 
     public static class Response extends ActionResponse {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfig.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfig.java
index b25e78677b3..09953818919 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfig.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfig.java
@@ -214,6 +214,7 @@ public class ClassificationConfig implements LenientlyParsedInferenceConfig, Str
             this.topClassesResultsField = config.topClassesResultsField;
             this.resultsField = config.resultsField;
             this.numTopFeatureImportanceValues = config.numTopFeatureImportanceValues;
+            this.predictionFieldType = config.predictionFieldType;
         }
 
         public Builder setNumTopClasses(Integer numTopClasses) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdate.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdate.java
index bb12c04ff5b..290bbd01c49 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdate.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdate.java
@@ -262,11 +262,15 @@ public class ClassificationConfigUpdate implements InferenceConfigUpdate {
             return this;
         }
 
-        private Builder setPredictionFieldType(String predictionFieldType) {
-            this.predictionFieldType = PredictionFieldType.fromString(predictionFieldType);
+        public Builder setPredictionFieldType(PredictionFieldType predictionFieldtype) {
+            this.predictionFieldType = predictionFieldtype;
             return this;
         }
 
+        private Builder setPredictionFieldType(String predictionFieldType) {
+            return setPredictionFieldType(PredictionFieldType.fromString(predictionFieldType));
+        }
+
         public ClassificationConfigUpdate build() {
             return new ClassificationConfigUpdate(numTopClasses,
                 resultsField,
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldType.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldType.java
index 88dfd211403..f0a8f08aa00 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldType.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldType.java
@@ -6,6 +6,7 @@
 
 package org.elasticsearch.xpack.core.ml.inference.trainedmodel;
 
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -57,6 +58,19 @@ public enum PredictionFieldType implements Writeable {
                 }
                 return areClose(value, 1.0D);
             case NUMBER:
+                if (Strings.isNullOrEmpty(stringRep)) {
+                    return value;
+                }
+                // Quick check to verify that the string rep is LIKELY a number
+                // Still handles the case where it throws and then returns the underlying value
+                if (stringRep.charAt(0) == '-' || Character.isDigit(stringRep.charAt(0))) {
+                    try {
+                        return Long.parseLong(stringRep);
+                    } catch (NumberFormatException nfe) {
+                        return value;
+                    }
+                }
+                return value;
             default:
                 return value;
         }
diff --git a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelActionRequestTests.java b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelActionRequestTests.java
index 80693c94be9..5b736307c01 100644
--- a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelActionRequestTests.java
+++ b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/action/InternalInferModelActionRequestTests.java
@@ -48,8 +48,8 @@ public class InternalInferModelActionRequestTests extends AbstractBWCWireSeriali
     }
 
     private static InferenceConfigUpdate randomInferenceConfigUpdate() {
-        return randomFrom(RegressionConfigUpdateTests.randomRegressionConfig(),
-            ClassificationConfigUpdateTests.randomClassificationConfig());
+        return randomFrom(RegressionConfigUpdateTests.randomRegressionConfigUpdate(),
+            ClassificationConfigUpdateTests.randomClassificationConfigUpdate());
     }
 
     private static Map<String, Object> randomMap() {
diff --git a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigTests.java b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigTests.java
index 8ffd1d7ff85..71658d74a12 100644
--- a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigTests.java
+++ b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigTests.java
@@ -29,6 +29,9 @@ public class ClassificationConfigTests extends AbstractBWCSerializationTestCase<
 
     public static ClassificationConfig mutateForVersion(ClassificationConfig instance, Version version) {
         ClassificationConfig.Builder builder = new ClassificationConfig.Builder(instance);
+        if (version.before(Version.V_7_8_0)) {
+            builder.setPredictionFieldType(PredictionFieldType.STRING);
+        }
         if (version.before(Version.V_7_7_0)) {
             builder.setNumTopFeatureImportanceValues(0);
         }
diff --git a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdateTests.java b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdateTests.java
index ff8bbe13251..c0c43f210e4 100644
--- a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdateTests.java
+++ b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ClassificationConfigUpdateTests.java
@@ -16,11 +16,12 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
+import static org.elasticsearch.xpack.core.ml.inference.trainedmodel.ClassificationConfigTests.randomClassificationConfig;
 import static org.hamcrest.Matchers.equalTo;
 
 public class ClassificationConfigUpdateTests extends AbstractBWCSerializationTestCase<ClassificationConfigUpdate> {
 
-    public static ClassificationConfigUpdate randomClassificationConfig() {
+    public static ClassificationConfigUpdate randomClassificationConfigUpdate() {
         return new ClassificationConfigUpdate(randomBoolean() ? null : randomIntBetween(-1, 10),
             randomBoolean() ? null : randomAlphaOfLength(10),
             randomBoolean() ? null : randomAlphaOfLength(10),
@@ -49,9 +50,33 @@ public class ClassificationConfigUpdateTests extends AbstractBWCSerializationTes
         assertThat(ex.getMessage(), equalTo("Unrecognized fields [some_key]."));
     }
 
+    public void testApply() {
+        ClassificationConfig originalConfig = randomClassificationConfig();
+
+        assertThat(originalConfig, equalTo(ClassificationConfigUpdate.EMPTY_PARAMS.apply(originalConfig)));
+
+        assertThat(new ClassificationConfig.Builder(originalConfig).setNumTopClasses(5).build(),
+            equalTo(new ClassificationConfigUpdate.Builder().setNumTopClasses(5).build().apply(originalConfig)));
+        assertThat(new ClassificationConfig.Builder()
+            .setNumTopClasses(5)
+            .setNumTopFeatureImportanceValues(1)
+            .setPredictionFieldType(PredictionFieldType.BOOLEAN)
+            .setResultsField("foo")
+            .setTopClassesResultsField("bar").build(),
+            equalTo(new ClassificationConfigUpdate.Builder()
+                .setNumTopClasses(5)
+                .setNumTopFeatureImportanceValues(1)
+                .setPredictionFieldType(PredictionFieldType.BOOLEAN)
+                .setResultsField("foo")
+                .setTopClassesResultsField("bar")
+                .build()
+                .apply(originalConfig)
+            ));
+    }
+
     @Override
     protected ClassificationConfigUpdate createTestInstance() {
-        return randomClassificationConfig();
+        return randomClassificationConfigUpdate();
     }
 
     @Override
diff --git a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldTypeTests.java b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldTypeTests.java
index ff8dd83cde2..0901ee62e74 100644
--- a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldTypeTests.java
+++ b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PredictionFieldTypeTests.java
@@ -38,6 +38,9 @@ public class PredictionFieldTypeTests extends ESTestCase {
             is(nullValue()));
         assertThat(PredictionFieldType.NUMBER.transformPredictedValue(1.0, "foo"), equalTo(1.0));
         assertThat(PredictionFieldType.NUMBER.transformPredictedValue(1.0, null), equalTo(1.0));
+        assertThat(PredictionFieldType.NUMBER.transformPredictedValue(1.0, ""), equalTo(1.0));
+        long expected = randomLong();
+        assertThat(PredictionFieldType.NUMBER.transformPredictedValue(1.0, String.valueOf(expected)), equalTo(expected));
     }
 
 }
diff --git a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/RegressionConfigUpdateTests.java b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/RegressionConfigUpdateTests.java
index 0d4212de9bd..fa9d33c617e 100644
--- a/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/RegressionConfigUpdateTests.java
+++ b/x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/RegressionConfigUpdateTests.java
@@ -16,11 +16,12 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
+import static org.elasticsearch.xpack.core.ml.inference.trainedmodel.RegressionConfigTests.randomRegressionConfig;
 import static org.hamcrest.Matchers.equalTo;
 
 public class RegressionConfigUpdateTests extends AbstractBWCSerializationTestCase<RegressionConfigUpdate> {
 
-    public static RegressionConfigUpdate randomRegressionConfig() {
+    public static RegressionConfigUpdate randomRegressionConfigUpdate() {
         return new RegressionConfigUpdate(randomBoolean() ? null : randomAlphaOfLength(10),
             randomBoolean() ? null : randomIntBetween(0, 10));
     }
@@ -40,9 +41,28 @@ public class RegressionConfigUpdateTests extends AbstractBWCSerializationTestCas
         assertThat(ex.getMessage(), equalTo("Unrecognized fields [some_key]."));
     }
 
+    public void testApply() {
+        RegressionConfig originalConfig = randomRegressionConfig();
+
+        assertThat(originalConfig, equalTo(RegressionConfigUpdate.EMPTY_PARAMS.apply(originalConfig)));
+
+        assertThat(new RegressionConfig.Builder(originalConfig).setNumTopFeatureImportanceValues(5).build(),
+            equalTo(new RegressionConfigUpdate.Builder().setNumTopFeatureImportanceValues(5).build().apply(originalConfig)));
+        assertThat(new RegressionConfig.Builder()
+                .setNumTopFeatureImportanceValues(1)
+                .setResultsField("foo")
+                .build(),
+            equalTo(new RegressionConfigUpdate.Builder()
+                .setNumTopFeatureImportanceValues(1)
+                .setResultsField("foo")
+                .build()
+                .apply(originalConfig)
+            ));
+    }
+
     @Override
     protected RegressionConfigUpdate createTestInstance() {
-        return randomRegressionConfig();
+        return randomRegressionConfigUpdate();
     }
 
     @Override