diff --git a/daffodil-lib/src/main/resources/org/apache/daffodil/xsd/tdml.xsd b/daffodil-lib/src/main/resources/org/apache/daffodil/xsd/tdml.xsd
index 6d4562f39c..8a8441a1e2 100644
--- a/daffodil-lib/src/main/resources/org/apache/daffodil/xsd/tdml.xsd
+++ b/daffodil-lib/src/main/resources/org/apache/daffodil/xsd/tdml.xsd
@@ -308,7 +308,15 @@
 
   <complexType name="dfdlInfosetType" mixed="true">
     <sequence>
-      <any namespace="##any" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
+      <!--
+      Can be empty if type is 'file'.
+      Otherwise, can be any single element (maxOccurs unbounded removed),
+      which is the root element of the infoset.
+
+      Mixed="true" because when type='file' the content is just a string
+      that is the file path
+      -->
+      <any namespace="##any" processContents="lax" minOccurs="0" maxOccurs="1"/>
     </sequence>
     <attribute name="type" use="optional" default="infoset">
       <simpleType>
diff --git a/daffodil-tdml-lib/src/main/scala/org/apache/daffodil/tdml/TDMLRunner.scala b/daffodil-tdml-lib/src/main/scala/org/apache/daffodil/tdml/TDMLRunner.scala
index 0cfe487d4f..ad25deacf6 100644
--- a/daffodil-tdml-lib/src/main/scala/org/apache/daffodil/tdml/TDMLRunner.scala
+++ b/daffodil-tdml-lib/src/main/scala/org/apache/daffodil/tdml/TDMLRunner.scala
@@ -31,6 +31,7 @@ import java.nio.charset.StandardCharsets
 import scala.collection.mutable
 import scala.language.postfixOps
 import scala.util.Try
+import scala.xml.Elem
 import scala.xml.Node
 import scala.xml.NodeSeq
 import scala.xml.NodeSeq.seqToNodeSeq
@@ -2769,41 +2770,52 @@ case class Infoset(i: NodeSeq, parent: TestCase) {
 
 case class DFDLInfoset(di: Node, parent: Infoset) {
 
-  private lazy val infosetNodeSeq = {
-    val testCase: TestCase = parent.parent
-    val loader = testCase.parent.loader
-    val optDataSchema: Option[URI] = {
-      testCase.optSchemaFileURI.orElse(testCase.optEmbeddedSchema.map { _.uriForLoading })
-    }
-    val src =
-      (di \ "@type").toString match {
-        case "infoset" | "" => {
-          val rawElem = di.child.filter {
-            _.isInstanceOf[scala.xml.Elem]
-          }.head
-          UnitTestSchemaSource(rawElem, testCase.tcName)
-        }
-        case "file" => {
-          val path = di.text.trim()
-          val maybeURI = parent.parent.parent.findTDMLResource(path)
-          val uri = maybeURI.getOrElse(
-            throw new FileNotFoundException(
-              "TDMLRunner: infoset file '" + path + "' was not found"
-            )
-          )
-          URISchemaSource(uriToDiagnosticFile(uri), uri)
-        }
-        case value => Assert.abort("Unknown value for type attribute on dfdlInfoset: " + value)
-      }
+  private lazy val testCase: TestCase = parent.parent
+  private lazy val loader = testCase.parent.loader
+  private val ty: String = {
+    val t = (di \ "@type").text.trim
+    if (t.isEmpty) "infoset" else t
+  }
+
+  private val elemOrStr: Either[Elem, String] = {
+    val (elems, others) = di.child.partition(_.isInstanceOf[scala.xml.Elem])
+    (elems, others.text.trim) match {
+      case (Seq(elem: Elem), "") if (ty == "infoset") => Left(elem)
+      case (Seq(), str) if (ty == "file") => Right(str)
+      case _ =>
+        Assert.usageError(
+          """dfdlInfoset element must contain a single root element or a file path (when 'type="file"')."""
+        )
+    }
+  }
+
+  lazy val contents: Elem = {
+    elemOrStr match {
+      case Left(elem) => elem
+      case Right(path) => infosetNodeFromFile(path)
+    }
+  }
+
+  private def infosetNodeFromFile(path: String): Elem = {
+
+    val maybeURI = parent.parent.parent.findTDMLResource(path)
+    val uri = maybeURI.getOrElse(
+      throw new FileNotFoundException(
+        "TDMLRunner: infoset file '" + path + "' was not found"
+      )
+    )
+    val infosetSrc = URISchemaSource(uriToDiagnosticFile(uri), uri)
+
+    val testSuite = testCase.parent
+    val before = testSuite.loadingExceptions.clone()
+
+    val elem = loader.load(infosetSrc, None) // no schema
     //
     // TODO: DAFFODIL-288 validate the infoset also
     // You can pass the optDataSchema, which appears to be the correct thing
     // but in many cases it doesn't seem to be able to resolve things.
     //
-    val testSuite = testCase.parent
-    val before = testSuite.loadingExceptions.clone()
-    // val elem: Node = loader.load(src, optDataSchema)
-    val elem = loader.load(src, None) // no schema
+    // val elem: Node = loader.load(infosetSrc, optDataSchema)
 
     // The expected infoset is loaded using the normalizeCRLFtoLF mode (which
     // is the default), so MS-DOS/Windows CRLFs in expected data XML files will
@@ -2818,17 +2830,9 @@ case class DFDLInfoset(di: Node, parent: Infoset) {
       val newExceptions = (testSuite.loadingExceptions -- before).toSeq
       testCase.toss(TDMLException(newExceptions, None), None)
     }
-    elem
+    elem.asInstanceOf[Elem]
   }
 
-  lazy val contents = {
-    Assert.usage(
-      infosetNodeSeq.size == 1,
-      "dfdlInfoset element must contain a single root element"
-    )
-    val c = infosetNodeSeq.head
-    c
-  }
 }
 
 object DiagnosticType extends Enumeration {
diff --git a/daffodil-tdml-lib/src/test/scala/org/apache/daffodil/tdml/UnitTestTDMLRunner.scala b/daffodil-tdml-lib/src/test/scala/org/apache/daffodil/tdml/UnitTestTDMLRunner.scala
index e4299c1a2f..c71ae205ff 100644
--- a/daffodil-tdml-lib/src/test/scala/org/apache/daffodil/tdml/UnitTestTDMLRunner.scala
+++ b/daffodil-tdml-lib/src/test/scala/org/apache/daffodil/tdml/UnitTestTDMLRunner.scala
@@ -21,6 +21,7 @@ import java.io.File
 
 import org.apache.daffodil.lib.Implicits._
 import org.apache.daffodil.lib.Implicits.using
+import org.apache.daffodil.lib.exceptions.UsageException
 import org.apache.daffodil.lib.util._
 import org.apache.daffodil.lib.xml.XMLUtils
 
@@ -336,6 +337,17 @@ class UnitTestTDMLRunner {
     assertEquals(expected, actual.toList)
   }
 
+  @Test def testDFDLInfosetEmptyDiagnosticMsg(): Unit = {
+    val xml = <tdml:dfdlInfoset/>
+    val exc = intercept[UsageException] {
+      val di = new DFDLInfoset(xml, null)
+      di.contents
+    }
+    val m = exc.getMessage
+    assertTrue(m.contains("dfdlInfoset"))
+    assertTrue(m.contains("single root element"))
+  }
+
   @Test def testLSB1(): Unit = {
     val xml = <document bitOrder="LSBFirst">
                 <documentPart type="bits">00000010</documentPart>
diff --git a/daffodil-tdml-processor/src/test/scala/org/apache/daffodil/processor/tdml/TestTDMLRunner.scala b/daffodil-tdml-processor/src/test/scala/org/apache/daffodil/processor/tdml/TestTDMLRunner.scala
index e2f346f23d..1d4ccf74d1 100644
--- a/daffodil-tdml-processor/src/test/scala/org/apache/daffodil/processor/tdml/TestTDMLRunner.scala
+++ b/daffodil-tdml-processor/src/test/scala/org/apache/daffodil/processor/tdml/TestTDMLRunner.scala
@@ -18,6 +18,7 @@
 package org.apache.daffodil.processor.tdml
 
 import java.io.File
+import java.io.FileNotFoundException
 
 import org.apache.daffodil.lib.Implicits._
 import org.apache.daffodil.lib.Implicits.using
@@ -1061,4 +1062,32 @@ f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff
     assertTrue(exc.getMessage.contains("Either tdml:infoset or tdml:error"))
     assertTrue(exc.getMessage.contains("must be present in the test"))
   }
+
+  @Test def testInfosetFileNotFound() = {
+    val testSuite =
+      <tdml:testSuite suiteName="theSuiteName" xmlns:tdml={tdml} xmlns:dfdl={dfdl}
+                      xmlns:xs={xsd}>
+        <tdml:defineSchema name="mySchema">
+          <xs:include schemaLocation="/org/apache/daffodil/xsd/DFDLGeneralFormat.dfdl.xsd"/>
+          <dfdl:format ref="GeneralFormat"/>
+          <xs:element name="data" type="xs:int" dfdl:lengthKind="delimited"/>
+        </tdml:defineSchema>
+        <tdml:unparserTestCase name="infosetFileNotFound" root="data" model="mySchema">
+          <tdml:infoset>
+            <tdml:dfdlInfoset type="file">/this/does/not/exist.xml</tdml:dfdlInfoset>
+          </tdml:infoset>
+          <tdml:document/>
+        </tdml:unparserTestCase>
+      </tdml:testSuite>
+
+    val runner = new Runner(testSuite)
+    val e = intercept[FileNotFoundException] {
+      runner.runOneTest("infosetFileNotFound")
+    }
+    runner.reset
+    val msg = e.getMessage()
+    assertTrue(msg.contains("not found"))
+    assertTrue(msg.contains("/this/does/not/exist.xml"))
+  }
+
 }
diff --git a/daffodil-test/src/test/resources/org/apache/daffodil/section15/choice_groups/HiddenChoices.tdml b/daffodil-test/src/test/resources/org/apache/daffodil/section15/choice_groups/HiddenChoices.tdml
index e4094ac652..f0b199022f 100644
--- a/daffodil-test/src/test/resources/org/apache/daffodil/section15/choice_groups/HiddenChoices.tdml
+++ b/daffodil-test/src/test/resources/org/apache/daffodil/section15/choice_groups/HiddenChoices.tdml
@@ -217,7 +217,7 @@
   <tdml:unparserTestCase name="nestedNoOVCinHiddenContext" root="e7"
     model="ChoicesInHiddenContexts.dfdl.xsd" description="hidden group ref">
     <tdml:infoset>
-      <tdml:dfdlInfoset>)
+      <tdml:dfdlInfoset>
         <ex:e7/>
       </tdml:dfdlInfoset>
     </tdml:infoset>