diff --git a/core/src/main/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderImpl.scala b/core/src/main/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderImpl.scala
index a461a452..2e04021b 100644
--- a/core/src/main/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderImpl.scala
+++ b/core/src/main/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderImpl.scala
@@ -183,5 +183,6 @@ private final class ProtoTranscoderImpl(
     if !emittedOptions then
       emittedOptions = true
       rowBuffer.append(RdfStreamRow(outputOptions.copy(
-        version = Constants.protoVersion
+        version = if inputOptions.version == Constants.protoVersionNoNsDecl then
+          Constants.protoVersionNoNsDecl else Constants.protoVersion,
       )))
diff --git a/core/src/test/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderSpec.scala b/core/src/test/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderSpec.scala
index c35f1ae5..cf5074a0 100644
--- a/core/src/test/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderSpec.scala
+++ b/core/src/test/scala/eu/ostrzyciel/jelly/core/ProtoTranscoderSpec.scala
@@ -202,6 +202,14 @@ class ProtoTranscoderSpec extends AnyWordSpec, Inspectors, Matchers:
         output(i) shouldBe expectedOutput(i)
     }
 
+    "maintain protocol version 1 if input uses it" in {
+      val options = JellyOptions.smallStrict.withVersion(Constants.protoVersionNoNsDecl)
+      val input = RdfStreamRow(options)
+      val transcoder = ProtoTranscoder.fastMergingTranscoderUnsafe(options.withVersion(Constants.protoVersion))
+      val output = transcoder.ingestRow(input)
+      output.head shouldBe input
+    }
+
     "throw an exception on a null row" in {
       val transcoder = ProtoTranscoder.fastMergingTranscoderUnsafe(JellyOptions.smallStrict)
       val ex = intercept[RdfProtoTranscodingError] {
diff --git a/integration-tests/src/test/resources/backcompat/riverbench_main_v1_1_0.jelly b/integration-tests/src/test/resources/backcompat/riverbench_main_v1_1_0.jelly
new file mode 100644
index 00000000..059a94e2
Binary files /dev/null and b/integration-tests/src/test/resources/backcompat/riverbench_main_v1_1_0.jelly differ
diff --git a/integration-tests/src/test/resources/backcompat/riverbench_nanopubs_v1_1_0.jelly b/integration-tests/src/test/resources/backcompat/riverbench_nanopubs_v1_1_0.jelly
new file mode 100644
index 00000000..18b3ebb2
Binary files /dev/null and b/integration-tests/src/test/resources/backcompat/riverbench_nanopubs_v1_1_0.jelly differ
diff --git a/integration-tests/src/test/resources/backcompat/weather_quads_v1_1_0.jelly b/integration-tests/src/test/resources/backcompat/weather_quads_v1_1_0.jelly
new file mode 100644
index 00000000..ab57a8db
Binary files /dev/null and b/integration-tests/src/test/resources/backcompat/weather_quads_v1_1_0.jelly differ
diff --git a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/BackCompatSpec.scala b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/BackCompatSpec.scala
index f2d649b7..967de958 100644
--- a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/BackCompatSpec.scala
+++ b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/BackCompatSpec.scala
@@ -2,25 +2,54 @@ package eu.ostrzyciel.jelly.integration_tests
 
 import eu.ostrzyciel.jelly.convert.jena.riot.JellyLanguage
 import eu.ostrzyciel.jelly.convert.jena.traits.JenaTest
+import eu.ostrzyciel.jelly.core.Constants
+import eu.ostrzyciel.jelly.core.proto.v1.*
 import org.apache.jena.riot.{Lang, RDFDataMgr}
 import org.apache.jena.sparql.core.DatasetGraphFactory
 import org.scalatest.concurrent.ScalaFutures
 import org.scalatest.matchers.should.Matchers
 import org.scalatest.wordspec.AnyWordSpec
 
+import java.io.File
 import scala.jdk.CollectionConverters.*
 
-class BackCompatSpec extends AnyWordSpec, Matchers, ScalaFutures, JenaTest:
-  private val testCases = Seq(
-    ("riverbench_main", "RiverBench main metadata", Seq("v1_0_0")),
-    ("riverbench_nanopubs", "RiverBench nanopubs dataset metadata", Seq("v1_0_0")),
-    ("weather_quads", "Jelly 1.0.0, weather data example (QUADS stream)", Seq("v1_0_0")),
+object BackCompatSpec:
+  val descriptions = Map(
+    "riverbench_main" -> "RiverBench main metadata",
+    "riverbench_nanopubs" -> "RiverBench nanopubs dataset metadata",
+    "weather_quads" -> "weather data example (QUADS stream)"
+  )
+
+  val versionToNumber = Map(
+    "v1_0_0" -> 1,
+    "v1_1_0" -> 2,
   )
 
+  lazy val testCases: Seq[(String, String, Seq[String])] =
+    File(getClass.getResource("/backcompat").toURI).listFiles().toSeq
+      .filter(_.getName.endsWith(".jelly"))
+      .map(f => (f.getName, f.getName.split("_v").head.split('.').head))
+      .groupBy(_._2)
+      .map { case (name, files) =>
+        val versions = files.map(f => "v" + f._1.split("_v").last.split('.').head).sorted
+        (name, descriptions(name), versions)
+      }
+      .toSeq
+
+class BackCompatSpec extends AnyWordSpec, Matchers, ScalaFutures, JenaTest:
+  import BackCompatSpec.*
+
+  val currentVersion = "v" + Constants.protoSemanticVersion.replace(".", "_")
+
   for (fileName, description, versions) <- testCases do
-  for version <- versions do
     s"Backward compatibility with $description" should {
-      s"be maintained for Jelly version $version when parsing" in {
+      s"be tested with the current version ($currentVersion)" in {
+        // If this test is failing, it means that you have to update this spec :)
+        // Go to util/MakeBackCompatTestCases.scala and run it. This should fix it.
+        versions should contain (currentVersion)
+      }
+
+      for version <- versions do s"be maintained for Jelly version $version when parsing" in {
         val jellyDg = DatasetGraphFactory.create()
         RDFDataMgr.read(
           jellyDg,
@@ -35,4 +64,10 @@ class BackCompatSpec extends AnyWordSpec, Matchers, ScalaFutures, JenaTest:
         )
         CrossStreamingSpec.compareDatasets(jellyDg, jenaDg)
       }
+
+      for version <- versions do s"work for $version, reading the correct version number from file" in {
+        val is = getClass.getResourceAsStream(s"/backcompat/${fileName}_$version.jelly")
+        val opt: RdfStreamOptions = RdfStreamFrame.parseDelimitedFrom(is).get.rows.head.row.options
+        opt.version should be (versionToNumber(version))
+      }
     }
diff --git a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/ForwardCompatSpec.scala b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/ForwardCompatSpec.scala
index e17a4ee6..c8d294d7 100644
--- a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/ForwardCompatSpec.scala
+++ b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/ForwardCompatSpec.scala
@@ -51,12 +51,12 @@ class ForwardCompatSpec extends AnyWordSpec, Matchers, ScalaFutures, JenaTest:
   private val futureFrameBytes2: Array[Byte] = futureFrame2.toByteArray
 
   "current Jelly version" should {
-    "be 1" in {
+    "be 2" in {
       // If this test is failing, it means that you have to update this spec :)
       // Go to integration-tests/src/main/protobuf and update the proto file to what you are using now.
       // Then, reintroduce the "future" changes that are tested here.
       // You can then update this test to the version number you are using.
-      Constants.protoVersion should be (1)
+      Constants.protoVersion should be (2)
     }
   }
 
diff --git a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/IoSerDesSpec.scala b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/IoSerDesSpec.scala
index c7934f05..811c89d7 100644
--- a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/IoSerDesSpec.scala
+++ b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/io/IoSerDesSpec.scala
@@ -85,7 +85,7 @@ class IoSerDesSpec extends AnyWordSpec, Matchers, ScalaFutures, JenaTest:
     options.maxNameTableSize should be (expOpt.maxNameTableSize)
     options.maxPrefixTableSize should be (expOpt.maxPrefixTableSize)
     options.maxDatatypeTableSize should be (expOpt.maxDatatypeTableSize)
-    options.version should be (Constants.protoVersion)
+    options.version should be (Constants.protoVersionNoNsDecl)
 
   runTest(JenaSerDes, JenaSerDes)
   runTest(JenaSerDes, JenaStreamSerDes)
diff --git a/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/util/MakeBackCompatTestCases.scala b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/util/MakeBackCompatTestCases.scala
new file mode 100644
index 00000000..852dbcef
--- /dev/null
+++ b/integration-tests/src/test/scala/eu/ostrzyciel/jelly/integration_tests/util/MakeBackCompatTestCases.scala
@@ -0,0 +1,39 @@
+package eu.ostrzyciel.jelly.integration_tests.util
+
+import eu.ostrzyciel.jelly.convert.jena.riot.{JellyFormatVariant, JellyLanguage}
+import eu.ostrzyciel.jelly.core.Constants
+import eu.ostrzyciel.jelly.integration_tests.BackCompatSpec.testCases
+import org.apache.jena.riot.{Lang, RDFDataMgr, RDFFormat}
+import org.apache.jena.sparql.core.DatasetGraphFactory
+
+import java.nio.file.{Files, Path}
+
+/**
+ * Utility to generate *.jelly files for later back-compat testing.
+ * These live in resources/backcompat.
+ *
+ * Run this utility after increasing the protocol version in the Constants class.
+ */
+object MakeBackCompatTestCases:
+
+  @main
+  def runMakeBackCompatTestCases(): Unit =
+    val version = Constants.protoSemanticVersion.replace(".", "_")
+    for (fileName, description, versions) <- testCases do
+      val jenaDg = DatasetGraphFactory.create()
+      RDFDataMgr.read(
+        jenaDg,
+        getClass.getResourceAsStream(s"/backcompat/$fileName.trig"),
+        Lang.TRIG
+      )
+      val v2Format = new RDFFormat(
+        JellyLanguage.JELLY,
+        // enable this to make this into a Jelly 1.1.0 file
+        JellyFormatVariant(enableNamespaceDeclarations = true)
+      )
+      RDFDataMgr.write(
+        Files.newOutputStream(Path.of(s"integration-tests/src/test/resources/backcompat/${fileName}_v$version.jelly")),
+        jenaDg,
+        v2Format
+      )
+      println(s"Generated ${fileName}_v$version.jelly")
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 9703326f..d66631ab 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
@@ -42,7 +42,8 @@ private[riot] object Util:
     baseVariant.copy(
       opt = context.get[RdfStreamOptions](JellyLanguage.SYMBOL_STREAM_OPTIONS, preset),
       frameSize = context.getInt(JellyLanguage.SYMBOL_FRAME_SIZE, baseVariant.frameSize),
-      enableNamespaceDeclarations = context.isTrue(JellyLanguage.SYMBOL_ENABLE_NAMESPACE_DECLARATIONS),
+      enableNamespaceDeclarations = context.isTrue(JellyLanguage.SYMBOL_ENABLE_NAMESPACE_DECLARATIONS) ||
+        baseVariant.enableNamespaceDeclarations,
     )
 
 /**