diff --git a/CHANGELOG.md b/CHANGELOG.md
index 35e8e01..46e238d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [Unreleased]
+
+### Changed
+
+- Krill metadata field names corrected by default: the misleadingly named `textClass` is now emitted as `dmozDomain` (DMOZ-based topic-domain classification) and `textDomain` as `idsColumn` (normalised newspaper column / Ressort). Pass `--legacy-field-names` to keep the historical names. Note: querying the corrected indices by the old names will require a need an accordingly configured Koral Mapper plugin to be active.
+
 ## [v3.4.0] - 2026-06-08
 
 ### Added
diff --git a/app/src/main/kotlin/de/ids_mannheim/korapxmltools/KorapXmlTool.kt b/app/src/main/kotlin/de/ids_mannheim/korapxmltools/KorapXmlTool.kt
index f178517..6529c9b 100644
--- a/app/src/main/kotlin/de/ids_mannheim/korapxmltools/KorapXmlTool.kt
+++ b/app/src/main/kotlin/de/ids_mannheim/korapxmltools/KorapXmlTool.kt
@@ -209,6 +209,12 @@
     var includeNonWordTokens: Boolean = false
 
     @Option(
+        names = ["--legacy-field-names"],
+        description = ["Keep historical Krill metadata field names instead of the corrected ones (textClass instead of dmozDomain, textDomain instead of idsColumn)."]
+    )
+    var legacyFieldNames: Boolean = false
+
+    @Option(
         names = ["--lz4"],
         description = ["Use LZ4 compression for Krill JSON output instead of gzip (faster but larger files)."]
     )
@@ -708,6 +714,7 @@
         if (useStaxTextParser)    sb.appendLine("  --stax-text")
         if (useLz4)               sb.appendLine("  --lz4")
         if (includeNonWordTokens) sb.appendLine("  --non-word-tokens")
+        if (legacyFieldNames)     sb.appendLine("  --legacy-field-names")
         if (sequentialInZip)      sb.appendLine("  --sequential")
         if (COMPATIBILITY_MODE)   sb.appendLine("  COMPATIBILITY_MODE=true")
 
@@ -6070,7 +6077,7 @@
             val byteOut = ByteArrayOutputStream()
             net.jpountz.lz4.LZ4FrameOutputStream(byteOut).use { lz4Out ->
                 OutputStreamWriter(lz4Out, StandardCharsets.UTF_8).use { writer ->
-                    KrillJsonGenerator.generateTo(writer, textData, corpusMetadata, docMetadata, includeNonWordTokens)
+                    KrillJsonGenerator.generateTo(writer, textData, corpusMetadata, docMetadata, includeNonWordTokens, legacyFieldNames)
                 }
             }
             Pair(fileName, byteOut.toByteArray())
@@ -6084,7 +6091,7 @@
             }
             gzipOut.use { gzip ->
                 OutputStreamWriter(gzip, StandardCharsets.UTF_8).use { writer ->
-                    KrillJsonGenerator.generateTo(writer, textData, corpusMetadata, docMetadata, includeNonWordTokens)
+                    KrillJsonGenerator.generateTo(writer, textData, corpusMetadata, docMetadata, includeNonWordTokens, legacyFieldNames)
                 }
             }
             Pair(fileName, byteOut.toByteArray())
diff --git a/app/src/main/kotlin/de/ids_mannheim/korapxmltools/formatters/KrillJsonGenerator.kt b/app/src/main/kotlin/de/ids_mannheim/korapxmltools/formatters/KrillJsonGenerator.kt
index e3fafea..cf22cbe 100644
--- a/app/src/main/kotlin/de/ids_mannheim/korapxmltools/formatters/KrillJsonGenerator.kt
+++ b/app/src/main/kotlin/de/ids_mannheim/korapxmltools/formatters/KrillJsonGenerator.kt
@@ -92,19 +92,31 @@
         textData: KrillTextData,
         corpusMetadata: Map<String, MutableMap<String, Any>>,
         docMetadata: Map<String, MutableMap<String, Any>>,
-        includeNonWordTokens: Boolean
+        includeNonWordTokens: Boolean,
+        legacyFieldNames: Boolean = false
     ): String {
         val sb = StringBuilder()
-        generateTo(sb, textData, corpusMetadata, docMetadata, includeNonWordTokens)
+        generateTo(sb, textData, corpusMetadata, docMetadata, includeNonWordTokens, legacyFieldNames)
         return sb.toString()
     }
 
+    // Krill metadata field keys that were named misleadingly early on. By default we
+    // emit the corrected names; the original names map to their proper meaning:
+    //   textClass  -> dmozDomain (DMOZ-based topic-domain classification)
+    //   textDomain -> idsColumn  (normalised newspaper column / Ressort)
+    // Pass legacyFieldNames=true to keep the historical keys.
+    private val CORRECTED_FIELD_NAMES = mapOf(
+        "textClass" to "dmozDomain",
+        "textDomain" to "idsColumn"
+    )
+
     fun generateTo(
         out: Appendable,
         textData: KrillTextData,
         corpusMetadata: Map<String, MutableMap<String, Any>>,
         docMetadata: Map<String, MutableMap<String, Any>>,
-        includeNonWordTokens: Boolean
+        includeNonWordTokens: Boolean,
+        legacyFieldNames: Boolean = false
     ) {
         val sb = StringBuilder()
         sb.append("{")
@@ -241,8 +253,9 @@
                 }
             }
 
+            val outKey = if (legacyFieldNames) key else CORRECTED_FIELD_NAMES[key] ?: key
             fields.add(jsonObject(listOf(
-                "key" to jsonString(key),
+                "key" to jsonString(outKey),
                 "@type" to jsonString("koral:field"),
                 "value" to fieldValue,
                 "type" to jsonString(fieldType)
diff --git a/app/src/test/kotlin/de/ids_mannheim/korapxmltools/KrillJsonGeneratorTest.kt b/app/src/test/kotlin/de/ids_mannheim/korapxmltools/KrillJsonGeneratorTest.kt
index 20f4971..1305a86 100644
--- a/app/src/test/kotlin/de/ids_mannheim/korapxmltools/KrillJsonGeneratorTest.kt
+++ b/app/src/test/kotlin/de/ids_mannheim/korapxmltools/KrillJsonGeneratorTest.kt
@@ -1253,4 +1253,30 @@
             "All categories present in the file should be indexed, in rank order"
         )
     }
+
+    @Test
+    fun correctedMetadataFieldNamesByDefault() {
+        val baseZip = loadResource("rei_sample.zip").path
+        val tar = ensureKrillTar("rei_corrected_names", "rei_sample.krill.tar") { outputDir ->
+            arrayOf("-t", "krill", "-q", "-D", outputDir.path, baseZip)
+        }
+        val json = readKrillJson(tar).entries.first { it.key.startsWith("REI-RBR-00473") }.value
+
+        // The misleadingly named textClass is emitted under its corrected name dmozDomain.
+        assertTrue(json.contains("\"key\":\"dmozDomain\""), "textClass should be emitted as dmozDomain by default")
+        assertFalse(json.contains("\"key\":\"textClass\""), "legacy textClass key must not appear by default")
+    }
+
+    @Test
+    fun legacyMetadataFieldNamesWithFlag() {
+        val baseZip = loadResource("rei_sample.zip").path
+        val tar = ensureKrillTar("rei_legacy_names", "rei_sample.krill.tar") { outputDir ->
+            arrayOf("-t", "krill", "-q", "--legacy-field-names", "-D", outputDir.path, baseZip)
+        }
+        val json = readKrillJson(tar).entries.first { it.key.startsWith("REI-RBR-00473") }.value
+
+        // With --legacy-field-names the historical key is kept and the corrected one is absent.
+        assertTrue(json.contains("\"key\":\"textClass\""), "--legacy-field-names should keep textClass")
+        assertFalse(json.contains("\"key\":\"dmozDomain\""), "corrected name must not appear in legacy mode")
+    }
 }