diff --git a/bson-multiplatform/src/commonMain/kotlin/serialization/MultiplatformDecoder.kt b/bson-multiplatform/src/commonMain/kotlin/serialization/MultiplatformDecoder.kt
index 42d48b7f..452c7121 100644
--- a/bson-multiplatform/src/commonMain/kotlin/serialization/MultiplatformDecoder.kt
+++ b/bson-multiplatform/src/commonMain/kotlin/serialization/MultiplatformDecoder.kt
@@ -196,9 +196,17 @@ internal class BsonCompositeDecoder(
 	val iterator = source.iterator()
 	lateinit var current: BsonDocument.Field
 	override fun decodeElementIndex(descriptor: SerialDescriptor): Int {
-		if (!iterator.hasNext()) return CompositeDecoder.DECODE_DONE
-		current = iterator.next()
-		return descriptor.getElementIndex(current.name)
+		// If we find some field that the descriptor doesn't know about,
+		// just skip it entirely, don't try to deserialize it.
+
+		while (iterator.hasNext()) {
+			current = iterator.next()
+			val index = descriptor.getElementIndex(current.name)
+			if (index != CompositeDecoder.UNKNOWN_NAME) {
+				return index
+			}
+		}
+		return CompositeDecoder.DECODE_DONE
 	}
 
 	override fun decodeBooleanElement(descriptor: SerialDescriptor, index: Int): Boolean {
diff --git a/bson-tests/src/commonMain/kotlin/BsonDocumentTests.kt b/bson-tests/src/commonMain/kotlin/BsonDocumentTests.kt
index db2d4f02..bd0caa00 100644
--- a/bson-tests/src/commonMain/kotlin/BsonDocumentTests.kt
+++ b/bson-tests/src/commonMain/kotlin/BsonDocumentTests.kt
@@ -113,6 +113,16 @@ fun SuiteDsl.verifyBsonDocuments(factory: Prepared<BsonFactory>) = suite("BSON d
 		check(exception.message matches "Could not decode opensavvy.ktmongo.bson.BsonDocumentUser.*\n\tfrom value \\{\"a\": \"Bob\"\\}.*\n*.*")
 	}
 
+	test("Decode a single document with additional fields (must be ignored)") {
+		val document = factory().buildDocument {
+			writeString("a", "Bob")
+			writeInt32("b", 45)
+			writeDouble("ignored", 2.3)
+		}
+
+		check(document.decode<BsonDocumentUser>() == BsonDocumentUser("Bob", 45))
+	}
+
 	test("Read a corrupt document") {
 		checkThrows<BsonDecodingException> {
 			// This document is malformed