diff --git a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/JenaStreamSerDes.scala b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/JenaStreamSerDes.scala
index f98b7336..d9c605df 100644
--- a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/JenaStreamSerDes.scala
+++ b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/JenaStreamSerDes.scala
@@ -56,7 +56,9 @@ object JenaStreamSerDes extends NativeSerDes[Seq[Triple], Seq[Quad]]:
 
   override def writeTriplesJelly(os: OutputStream, model: Seq[Triple], opt: RdfStreamOptions, frameSize: Int): Unit =
     val context = RIOT.getContext.copy()
-      .set(JellyLanguage.SYMBOL_STREAM_OPTIONS, opt.withPhysicalType(PhysicalStreamType.TRIPLES))
+      // Not setting the physical type, as it should be inferred from the data.
+      // This emulates how RIOT initializes the stream writer in practice.
+      .set(JellyLanguage.SYMBOL_STREAM_OPTIONS, opt)
       .set(JellyLanguage.SYMBOL_FRAME_SIZE, frameSize)
 
     val writerStream = StreamRDFWriter.getWriterStream(os, JellyLanguage.JELLY, context)
@@ -66,7 +68,7 @@ object JenaStreamSerDes extends NativeSerDes[Seq[Triple], Seq[Quad]]:
 
   override def writeQuadsJelly(os: OutputStream, dataset: Seq[Quad], opt: RdfStreamOptions, frameSize: Int): Unit =
     val context = RIOT.getContext.copy()
-      .set(JellyLanguage.SYMBOL_STREAM_OPTIONS, opt.withPhysicalType(PhysicalStreamType.QUADS))
+      .set(JellyLanguage.SYMBOL_STREAM_OPTIONS, opt)
       .set(JellyLanguage.SYMBOL_FRAME_SIZE, frameSize)
 
     val writerStream = StreamRDFWriter.getWriterStream(os, JellyLanguage.JELLY, context)
diff --git a/jena/src/main/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriter.scala b/jena/src/main/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriter.scala
index ff0f301a..bb47a577 100644
--- a/jena/src/main/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriter.scala
+++ b/jena/src/main/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriter.scala
@@ -92,7 +92,7 @@ final class JellyDatasetWriter(opt: JellyFormatVariant) extends WriterDatasetRIO
 object JellyStreamWriterFactory extends StreamRDFWriterFactory:
   override def create(out: OutputStream, format: RDFFormat, context: Context): StreamRDF =
     val variant = Util.getVariant(format)
-    JellyStreamWriter(
+    JellyStreamWriterAutodetectType(
       variant.copy(
         opt = context.get[RdfStreamOptions](JellyLanguage.SYMBOL_STREAM_OPTIONS, variant.opt),
         frameSize = context.getInt(JellyLanguage.SYMBOL_FRAME_SIZE, variant.frameSize),
@@ -100,6 +100,41 @@ object JellyStreamWriterFactory extends StreamRDFWriterFactory:
       out
     )
 
+/**
+ * Wrapper on JellyStreamWriter that autodetects the physical stream type based on the first element
+ * (triple or quad) added to the stream.
+ *
+ * This is used when initializing the stream writer with the RIOT APIs, where the stream type is not known.
+ *
+ * @param opt Jelly format variant
+ * @param out output stream
+ */
+final class JellyStreamWriterAutodetectType(opt: JellyFormatVariant, out: OutputStream) extends StreamRDF:
+  private var inner: JellyStreamWriter = null
+
+  override def start(): Unit = ()
+
+  override def triple(triple: Triple): Unit =
+    if inner == null then
+      inner = JellyStreamWriter(opt.copy(
+        opt = opt.opt.withPhysicalType(PhysicalStreamType.TRIPLES),
+      ), out)
+    inner.triple(triple)
+
+  override def quad(quad: Quad): Unit =
+    if inner == null then
+      inner = JellyStreamWriter(opt.copy(
+        opt = opt.opt.withPhysicalType(PhysicalStreamType.QUADS),
+      ), out)
+    inner.quad(quad)
+
+  override def base(base: String): Unit = ()
+
+  override def prefix(prefix: String, iri: String): Unit = ()
+
+  override def finish(): Unit =
+    if inner != null then
+      inner.finish()
 
 /**
  * A stream writer that writes RDF data in Jelly format.
diff --git a/jena/src/test/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriterSpec.scala b/jena/src/test/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriterSpec.scala
new file mode 100644
index 00000000..1b0af812
--- /dev/null
+++ b/jena/src/test/scala/eu/ostrzyciel/jelly/convert/jena/riot/JellyWriterSpec.scala
@@ -0,0 +1,71 @@
+package eu.ostrzyciel.jelly.convert.jena.riot
+
+import eu.ostrzyciel.jelly.convert.jena.traits.JenaTest
+import org.apache.commons.io.output.NullWriter
+import org.apache.jena.riot.RiotException
+import org.scalatest.matchers.should.Matchers
+import org.scalatest.wordspec.AnyWordSpec
+
+import java.io.OutputStream
+
+/**
+ * Tests covering rare edge cases in the Jelly writer.
+ * The main tests are done in the integration-tests module.
+ */
+class JellyWriterSpec extends AnyWordSpec, Matchers, JenaTest:
+  val streamWriters = Seq(
+    ("JellyStreamWriter", (opt, out) => JellyStreamWriter(opt, out)),
+    ("JellyStreamWriterAutodetectType", (opt, out) => JellyStreamWriterAutodetectType(opt, out)),
+  )
+
+  for (writerName, writerFactory) <- streamWriters do
+    f"$writerName" should {
+      for op <- Seq("start", "base", "prefix") do
+        f"do nothing on $op()" in {
+          var mutations = 0
+          val out = new OutputStream {
+            override def write(b: Int): Unit = mutations += 1
+          }
+          val writer = writerFactory(JellyFormatVariant(), out)
+          op match
+            case "start" => writer.start()
+            case "base" => writer.base("http://example.com")
+            case "prefix" => writer.prefix("ex", "http://example.com")
+          mutations should be (0)
+        }
+    }
+
+  "JellyStreamWriterAutodetectType" should {
+    "do nothing if the stream was not started" in {
+      val out = new OutputStream {
+        override def write(b: Int): Unit = fail("Should not write anything")
+      }
+      val writer = JellyStreamWriterAutodetectType(JellyFormatVariant(), out)
+      writer.finish()
+    }
+  }
+
+  val classicWriters: Seq[(String, JellyFormatVariant => JellyGraphWriter | JellyDatasetWriter)] = Seq(
+    ("JellyGraphWriter", (opt) => JellyGraphWriter(opt)),
+    ("JellyDatasetWriter", (opt) => JellyDatasetWriter(opt)),
+  )
+
+  for (writerName, writerFactory) <- classicWriters do
+    f"$writerName" should {
+      "throw an exception when writing to a Java Writer" in {
+        val writer = writerFactory(JellyFormatVariant())
+        val javaWriter = NullWriter.INSTANCE
+        intercept[RiotException] {
+          writer match
+            case graphWriter: JellyGraphWriter => graphWriter.write(javaWriter, null, null, null, null)
+            case datasetWriter: JellyDatasetWriter => datasetWriter.write(javaWriter, null, null, null, null)
+        }.getMessage should include ("Writing binary data to a java.io.Writer is not supported")
+      }
+
+      ".getLang return JellyLanguage.JELLY" in {
+        val writer = writerFactory(JellyFormatVariant())
+        writer match
+          case graphWriter: JellyGraphWriter => graphWriter.getLang should be (JellyLanguage.JELLY)
+          case datasetWriter: JellyDatasetWriter => datasetWriter.getLang should be (JellyLanguage.JELLY)
+      }
+    }