diff --git a/functions/errors.go b/functions/errors.go
index 709bfd9..23d7bcf 100644
--- a/functions/errors.go
+++ b/functions/errors.go
@@ -24,9 +24,27 @@ func (e ErrAlreadyRegistered) Error() string {
 
 // ErrValidation occurs when function payload doesn't validate.
 type ErrValidation struct {
-	original string
+	message string
 }
 
 func (e ErrValidation) Error() string {
-	return fmt.Sprintf("Function doesn't validate. Validation error: %q", e.original)
+	return fmt.Sprintf("Function doesn't validate. Validation error: %q", e.message)
+}
+
+// ErrFunctionCallFailed occurs when function call failed because of provider error.
+type ErrFunctionCallFailed struct {
+	original error
+}
+
+func (e ErrFunctionCallFailed) Error() string {
+	return fmt.Sprintf("Function call failed. Error: %q", e.original)
+}
+
+// ErrFunctionCallFailedProviderError occurs when function call failed because of provider error.
+type ErrFunctionCallFailedProviderError struct {
+	original error
+}
+
+func (e ErrFunctionCallFailedProviderError) Error() string {
+	return fmt.Sprintf("Function call failed because of provider error. Error: %q", e.original)
 }
diff --git a/functions/types.go b/functions/types.go
index edc7e26..e4ee0e6 100644
--- a/functions/types.go
+++ b/functions/types.go
@@ -3,6 +3,7 @@ package functions
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"io/ioutil"
 	"math/rand"
 	"net/http"
@@ -12,6 +13,7 @@ import (
 	validator "gopkg.in/go-playground/validator.v9"
 
 	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/lambda"
@@ -124,6 +126,16 @@ func (f *Function) callAWSLambda(payload []byte) ([]byte, error) {
 		FunctionName: &f.Provider.ARN,
 		Payload:      payload,
 	})
+	if err != nil {
+		if awserr, ok := err.(awserr.Error); ok {
+			switch awserr.Code() {
+			case lambda.ErrCodeServiceException:
+				return nil, &ErrFunctionCallFailedProviderError{awserr}
+			default:
+				return nil, &ErrFunctionCallFailed{awserr}
+			}
+		}
+	}
 
 	return invokeOutput.Payload, err
 }
@@ -135,10 +147,13 @@ func (f *Function) callHTTP(payload []byte) ([]byte, error) {
 
 	resp, err := client.Post(f.Provider.URL, "application/json", bytes.NewReader(payload))
 	if err != nil {
-		return []byte{}, err
+		return nil, &ErrFunctionCallFailed{err}
+	}
+	if resp.StatusCode == http.StatusInternalServerError {
+		return nil, &ErrFunctionCallFailedProviderError{fmt.Errorf("HTTP status code: %d", http.StatusInternalServerError)}
 	}
-	defer resp.Body.Close()
 
+	defer resp.Body.Close()
 	return ioutil.ReadAll(resp.Body)
 }
 
diff --git a/router/event.go b/router/event.go
index 65f6363..9d392c4 100644
--- a/router/event.go
+++ b/router/event.go
@@ -10,8 +10,8 @@ import (
 	"github.com/serverless/event-gateway/pubsub"
 )
 
-// Schema is a default event schema. All data that passes through the Event Gateway is formatted as an Event, based on this schema.
-type Schema struct {
+// Event is a default event structure. All data that passes through the Event Gateway is formatted as an Event, based on this schema.
+type Event struct {
 	Event      string      `json:"event"`
 	ID         string      `json:"id"`
 	ReceivedAt uint64      `json:"receivedAt"`
@@ -19,8 +19,19 @@ type Schema struct {
 	DataType   string      `json:"dataType"`
 }
 
-// HTTPSchema is a event schema used for sending events to HTTP subscriptions.
-type HTTPSchema struct {
+// NewEvent return new instance of Event.
+func NewEvent(name, mime string, payload interface{}) *Event {
+	return &Event{
+		Event:      name,
+		ID:         uuid.NewV4().String(),
+		ReceivedAt: uint64(time.Now().UnixNano() / int64(time.Millisecond)),
+		DataType:   mime,
+		Data:       payload,
+	}
+}
+
+// HTTPEvent is a event schema used for sending events to HTTP subscriptions.
+type HTTPEvent struct {
 	Headers map[string][]string `json:"headers"`
 	Query   map[string][]string `json:"query"`
 	Body    interface{}         `json:"body"`
@@ -31,7 +42,7 @@ const (
 	mimeOctetStrem = "application/octet-stream"
 )
 
-func fromRequest(r *http.Request) (*Schema, error) {
+func fromRequest(r *http.Request) (*Event, error) {
 	name := r.Header.Get("event")
 	if name == "" {
 		name = eventHTTP
@@ -47,13 +58,7 @@ func fromRequest(r *http.Request) (*Schema, error) {
 		return nil, err
 	}
 
-	event := &Schema{
-		Event:      name,
-		ID:         uuid.NewV4().String(),
-		ReceivedAt: uint64(time.Now().UnixNano() / int64(time.Millisecond)),
-		DataType:   mime,
-		Data:       body,
-	}
+	event := NewEvent(name, mime, body)
 
 	if mime == mimeJSON && len(body) > 0 {
 		err := json.Unmarshal(body, &event.Data)
@@ -63,7 +68,7 @@ func fromRequest(r *http.Request) (*Schema, error) {
 	}
 
 	if event.Event == eventHTTP {
-		event.Data = &HTTPSchema{
+		event.Data = &HTTPEvent{
 			Headers: r.Header,
 			Query:   r.URL.Query(),
 			Body:    event.Data,
diff --git a/router/integration_test.go b/router/integration_test.go
index 2926b64..865c6cd 100644
--- a/router/integration_test.go
+++ b/router/integration_test.go
@@ -55,7 +55,7 @@ func TestIntegrationSubscription(t *testing.T) {
 		func(w http.ResponseWriter, r *http.Request) {
 			reqBuf, _ := ioutil.ReadAll(r.Body)
 
-			var event Schema
+			var event Event
 			err := json.Unmarshal(reqBuf, &event)
 			if err != nil {
 				panic(err)
diff --git a/router/router.go b/router/router.go
index b27fa99..a84a094 100644
--- a/router/router.go
+++ b/router/router.go
@@ -150,6 +150,8 @@ const (
 
 	// headerFunctionID is a header name for specifing function id for sync invocation.
 	headerFunctionID = "function-id"
+
+	internalFunctionProviderError = "gateway.warn.functionProviderError"
 )
 
 var (
@@ -157,7 +159,7 @@ var (
 	errUnableToLookUpRegisteredFunction = errors.New("unable to look up registered function")
 )
 
-func (router *Router) handleHTTPEvent(event *Schema, w http.ResponseWriter, r *http.Request) {
+func (router *Router) handleHTTPEvent(event *Event, w http.ResponseWriter, r *http.Request) {
 	payload, err := json.Marshal(event)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
@@ -186,7 +188,7 @@ func (router *Router) handleHTTPEvent(event *Schema, w http.ResponseWriter, r *h
 	}
 }
 
-func (router *Router) handleEvent(instance *Schema, w http.ResponseWriter, r *http.Request) {
+func (router *Router) handleEvent(instance *Event, w http.ResponseWriter, r *http.Request) {
 	payload, err := json.Marshal(instance)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
@@ -261,13 +263,23 @@ func (router *Router) callFunction(backingFunctionID functions.FunctionID, paylo
 		return []byte{}, errUnableToLookUpRegisteredFunction
 	}
 
-	result, err := f.Call(payload)
-	if err != nil {
-		resErr := errors.New("unable to reach backing function: " + err.Error())
-		return []byte{}, resErr
+	resp, err := f.Call(payload)
+
+	if _, ok := err.(*functions.ErrFunctionCallFailedProviderError); ok {
+		internal := NewEvent(internalFunctionProviderError, mimeJSON, struct {
+			FunctionID string `json:"functionId"`
+		}{string(backingFunctionID)})
+		payload, err = json.Marshal(internal)
+		if err == nil {
+			router.log.Debug("Event received.", zap.String("event", string(payload)))
+			router.processEvent(event{
+				topics:  []pubsub.TopicID{pubsub.TopicID(internal.Event)},
+				payload: payload,
+			})
+		}
 	}
 
-	return result, nil
+	return resp, err
 }
 
 // loop is the main loop for a pub/sub worker goroutine
@@ -308,9 +320,7 @@ func (router *Router) loop() {
 	}
 }
 
-// processEvent sends event to a set of topics,
-// and for each of the functions that get called
-// as part of those topics.
+// processEvent sends event to a set of topics, and for each of the functions that get called as part of those topics.
 func (router *Router) processEvent(e event) {
 	for _, topicID := range e.topics {
 		subscribers := router.targetCache.SubscribersOfTopic(topicID)
@@ -349,14 +359,12 @@ func (router *Router) enqueueWork(topicMap map[pubsub.TopicID]struct{}, payload
 		payload: payload,
 	}:
 	default:
-		// We could not submit any work, this is NOT good but
-		// we will sacrifice consistency for availability for now.
+		// We could not submit any work, this is NOT good but we will sacrifice consistency for availability for now.
 		router.dropMetric.Inc()
 	}
 }
 
-// isDraining returns true if this Router is being drained of items
-// in its work queue before shutting down.
+// isDraining returns true if this Router is being drained of items in its work queue before shutting down.
 func (router *Router) isDraining() bool {
 	select {
 	case <-router.drain: