diff --git a/core/src/main/scala/org/apache/spark/internal/io/FileCommitProtocol.scala b/core/src/main/scala/org/apache/spark/internal/io/FileCommitProtocol.scala
index 6d0059b6a0272..e6e9c9e328853 100644
--- a/core/src/main/scala/org/apache/spark/internal/io/FileCommitProtocol.scala
+++ b/core/src/main/scala/org/apache/spark/internal/io/FileCommitProtocol.scala
@@ -20,6 +20,7 @@ package org.apache.spark.internal.io
 import org.apache.hadoop.fs._
 import org.apache.hadoop.mapreduce._
 
+import org.apache.spark.internal.Logging
 import org.apache.spark.util.Utils
 
 
@@ -132,7 +133,7 @@ abstract class FileCommitProtocol {
 }
 
 
-object FileCommitProtocol {
+object FileCommitProtocol extends Logging {
   class TaskCommitMessage(val obj: Any) extends Serializable
 
   object EmptyTaskCommitMessage extends TaskCommitMessage(null)
@@ -145,15 +146,23 @@ object FileCommitProtocol {
       jobId: String,
       outputPath: String,
       dynamicPartitionOverwrite: Boolean = false): FileCommitProtocol = {
+
+    logDebug(s"Creating committer $className; job $jobId; output=$outputPath;" +
+      s" dynamic=$dynamicPartitionOverwrite")
     val clazz = Utils.classForName(className).asInstanceOf[Class[FileCommitProtocol]]
     // First try the constructor with arguments (jobId: String, outputPath: String,
     // dynamicPartitionOverwrite: Boolean).
     // If that doesn't exist, try the one with (jobId: string, outputPath: String).
     try {
       val ctor = clazz.getDeclaredConstructor(classOf[String], classOf[String], classOf[Boolean])
+      logDebug("Using (String, String, Boolean) constructor")
       ctor.newInstance(jobId, outputPath, dynamicPartitionOverwrite.asInstanceOf[java.lang.Boolean])
     } catch {
       case _: NoSuchMethodException =>
+        logDebug("Falling back to (String, String) constructor")
+        require(!dynamicPartitionOverwrite,
+          "Dynamic Partition Overwrite is enabled but" +
+            s" the committer ${className} does not have the appropriate constructor")
         val ctor = clazz.getDeclaredConstructor(classOf[String], classOf[String])
         ctor.newInstance(jobId, outputPath)
     }
diff --git a/core/src/test/scala/org/apache/spark/internal/io/FileCommitProtocolInstantiationSuite.scala b/core/src/test/scala/org/apache/spark/internal/io/FileCommitProtocolInstantiationSuite.scala
new file mode 100644
index 0000000000000..2bd32fc927e21
--- /dev/null
+++ b/core/src/test/scala/org/apache/spark/internal/io/FileCommitProtocolInstantiationSuite.scala
@@ -0,0 +1,148 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.internal.io
+
+import org.apache.spark.SparkFunSuite
+
+/**
+ * Unit tests for instantiation of FileCommitProtocol implementations.
+ */
+class FileCommitProtocolInstantiationSuite extends SparkFunSuite {
+
+  test("Dynamic partitions require appropriate constructor") {
+
+    // you cannot instantiate a two-arg client with dynamic partitions
+    // enabled.
+    val ex = intercept[IllegalArgumentException] {
+      instantiateClassic(true)
+    }
+    // check the contents of the message and rethrow if unexpected.
+    // this preserves the stack trace of the unexpected
+    // exception.
+    if (!ex.toString.contains("Dynamic Partition Overwrite")) {
+      fail(s"Wrong text in caught exception $ex", ex)
+    }
+  }
+
+  test("Standard partitions work with classic constructor") {
+    instantiateClassic(false)
+  }
+
+  test("Three arg constructors have priority") {
+    assert(3 == instantiateNew(false).argCount,
+      "Wrong constructor argument count")
+  }
+
+  test("Three arg constructors have priority when dynamic") {
+    assert(3 == instantiateNew(true).argCount,
+      "Wrong constructor argument count")
+  }
+
+  test("The protocol must be of the correct class") {
+    intercept[ClassCastException] {
+      FileCommitProtocol.instantiate(
+        classOf[Other].getCanonicalName,
+        "job",
+        "path",
+        false)
+    }
+  }
+
+  test("If there is no matching constructor, class hierarchy is irrelevant") {
+    intercept[NoSuchMethodException] {
+      FileCommitProtocol.instantiate(
+        classOf[NoMatchingArgs].getCanonicalName,
+        "job",
+        "path",
+        false)
+    }
+  }
+
+  /**
+   * Create a classic two-arg protocol instance.
+   * @param dynamic dyanmic partitioning mode
+   * @return the instance
+   */
+  private def instantiateClassic(dynamic: Boolean): ClassicConstructorCommitProtocol = {
+    FileCommitProtocol.instantiate(
+      classOf[ClassicConstructorCommitProtocol].getCanonicalName,
+      "job",
+      "path",
+      dynamic).asInstanceOf[ClassicConstructorCommitProtocol]
+  }
+
+  /**
+   * Create a three-arg protocol instance.
+   * @param dynamic dyanmic partitioning mode
+   * @return the instance
+   */
+  private def instantiateNew(
+    dynamic: Boolean): FullConstructorCommitProtocol = {
+    FileCommitProtocol.instantiate(
+      classOf[FullConstructorCommitProtocol].getCanonicalName,
+      "job",
+      "path",
+      dynamic).asInstanceOf[FullConstructorCommitProtocol]
+  }
+
+}
+
+/**
+ * This protocol implementation does not have the new three-arg
+ * constructor.
+ */
+private class ClassicConstructorCommitProtocol(arg1: String, arg2: String)
+  extends HadoopMapReduceCommitProtocol(arg1, arg2) {
+}
+
+/**
+ * This protocol implementation does have the new three-arg constructor
+ * alongside the original, and a 4 arg one for completeness.
+ * The final value of the real constructor is the number of arguments
+ * used in the 2- and 3- constructor, for test assertions.
+ */
+private class FullConstructorCommitProtocol(
+  arg1: String,
+  arg2: String,
+  b: Boolean,
+  val argCount: Int)
+  extends HadoopMapReduceCommitProtocol(arg1, arg2, b) {
+
+  def this(arg1: String, arg2: String) = {
+    this(arg1, arg2, false, 2)
+  }
+
+  def this(arg1: String, arg2: String, b: Boolean) = {
+    this(arg1, arg2, false, 3)
+  }
+}
+
+/**
+ * This has the 2-arity constructor, but isn't the right class.
+ */
+private class Other(arg1: String, arg2: String) {
+
+}
+
+/**
+ * This has no matching arguments as well as being the wrong class.
+ */
+private class NoMatchingArgs() {
+
+}
+