diff --git a/src/org/intellij/markdown/flavours/gfm/GFMFlavourDescriptor.kt b/src/org/intellij/markdown/flavours/gfm/GFMFlavourDescriptor.kt
index 54adda32..cef4db10 100644
--- a/src/org/intellij/markdown/flavours/gfm/GFMFlavourDescriptor.kt
+++ b/src/org/intellij/markdown/flavours/gfm/GFMFlavourDescriptor.kt
@@ -19,7 +19,7 @@ import org.intellij.markdown.parser.sequentialparsers.impl.*
 import java.io.Reader
 import java.net.URI
 
-class GFMFlavourDescriptor : CommonMarkFlavourDescriptor() {
+open class GFMFlavourDescriptor : CommonMarkFlavourDescriptor() {
     override val markerProcessorFactory = GFMMarkerProcessor.Factory
 
     override fun createInlinesLexer(): MarkdownLexer {