diff --git a/router-protobuf/src/main/kotlin/io/moia/router/proto/ProtoDeserializationHandler.kt b/router-protobuf/src/main/kotlin/io/moia/router/proto/ProtoDeserializationHandler.kt
index 73af0469..83f05eb0 100644
--- a/router-protobuf/src/main/kotlin/io/moia/router/proto/ProtoDeserializationHandler.kt
+++ b/router-protobuf/src/main/kotlin/io/moia/router/proto/ProtoDeserializationHandler.kt
@@ -14,7 +14,7 @@ class ProtoDeserializationHandler : DeserializationHandler {
     private val proto = MediaType.parse("application/x-protobuf")
 
     override fun supports(input: APIGatewayProxyRequestEvent): Boolean =
-        MediaType.parse(input.contentType()).`is`(proto)
+        input.contentType() != null && MediaType.parse(input.contentType()).`is`(proto)
 
     override fun deserialize(input: APIGatewayProxyRequestEvent, target: KType?): Any {
         val bytes = Base64.getDecoder().decode(input.body)
diff --git a/router-protobuf/src/test/kotlin/io/moia/router/proto/ProtoDeserializationHandlerTest.kt b/router-protobuf/src/test/kotlin/io/moia/router/proto/ProtoDeserializationHandlerTest.kt
new file mode 100644
index 00000000..d90bc7fa
--- /dev/null
+++ b/router-protobuf/src/test/kotlin/io/moia/router/proto/ProtoDeserializationHandlerTest.kt
@@ -0,0 +1,25 @@
+package io.moia.router.proto
+
+import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent
+import io.moia.router.withHeader
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.Test
+
+internal class ProtoDeserializationHandlerTest {
+
+    @Test
+    fun `Deserializer should not support if the content type of the input is null`() {
+        assertFalse(ProtoDeserializationHandler().supports(APIGatewayProxyRequestEvent()))
+    }
+
+    @Test
+    fun `Deserializer should not support if the content type of the input is json`() {
+        assertFalse(ProtoDeserializationHandler().supports(APIGatewayProxyRequestEvent().withHeader("content-type", "application/json")))
+    }
+
+    @Test
+    fun `Deserializer should support if the content type of the input is protobuf`() {
+        assertTrue(ProtoDeserializationHandler().supports(APIGatewayProxyRequestEvent().withHeader("content-type", "application/x-protobuf")))
+    }
+}
\ No newline at end of file
diff --git a/router-protobuf/src/test/kotlin/io/moia/router/proto/RequestHandlerTest.kt b/router-protobuf/src/test/kotlin/io/moia/router/proto/RequestHandlerTest.kt
index ea8713f5..45cf7d80 100644
--- a/router-protobuf/src/test/kotlin/io/moia/router/proto/RequestHandlerTest.kt
+++ b/router-protobuf/src/test/kotlin/io/moia/router/proto/RequestHandlerTest.kt
@@ -14,7 +14,7 @@ import java.util.Base64
 
 class RequestHandlerTest {
 
-    val testRequestHandler = TestRequestHandler()
+    private val testRequestHandler = TestRequestHandler()
 
     @Test
     fun `should match request to proto handler and return json`() {