diff --git a/api/agent/protocol/http.go b/api/agent/protocol/http.go
index ea2761e0c..fdc6c6646 100644
--- a/api/agent/protocol/http.go
+++ b/api/agent/protocol/http.go
@@ -3,8 +3,11 @@ package protocol
 import (
 	"bufio"
 	"context"
+	"fmt"
 	"io"
 	"net/http"
+
+	"github.com/fnproject/fn/api/models"
 )
 
 // HTTPProtocol converts stdin/stdout streams into HTTP/1.1 compliant
@@ -37,7 +40,7 @@ func (h *HTTPProtocol) Dispatch(ctx context.Context, ci CallInfo, w io.Writer) e
 
 	resp, err := http.ReadResponse(bufio.NewReader(h.out), ci.Request())
 	if err != nil {
-		return err
+		return models.NewAPIError(http.StatusBadGateway, fmt.Errorf("invalid http response from function err: %v", err))
 	}
 	defer resp.Body.Close()
 
diff --git a/api/agent/protocol/json.go b/api/agent/protocol/json.go
index e601c9675..8bf1bdf6d 100644
--- a/api/agent/protocol/json.go
+++ b/api/agent/protocol/json.go
@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+
+	"github.com/fnproject/fn/api/models"
 )
 
 // This is sent into the function
@@ -197,7 +199,7 @@ func (h *JSONProtocol) Dispatch(ctx context.Context, ci CallInfo, w io.Writer) e
 	jout := new(jsonOut)
 	dec := json.NewDecoder(h.out)
 	if err := dec.Decode(jout); err != nil {
-		return fmt.Errorf("error decoding JSON from user function: %v", err)
+		return models.NewAPIError(http.StatusBadGateway, fmt.Errorf("invalid json response from function err: %v", err))
 	}
 	if rw, ok := w.(http.ResponseWriter); ok {
 		// this has to be done for pulling out:
diff --git a/api/server/runner_test.go b/api/server/runner_test.go
index 7ecba9a4b..63c4c5bf1 100644
--- a/api/server/runner_test.go
+++ b/api/server/runner_test.go
@@ -132,6 +132,7 @@ func TestRouteRunnerExecution(t *testing.T) {
 		[]*models.Route{
 			{Path: "/", AppName: "myapp", Image: "fnproject/fn-test-utils", Type: "sync", Memory: 128, Timeout: 30, IdleTimeout: 30, Headers: map[string][]string{"X-Function": {"Test"}}},
 			{Path: "/myhot", AppName: "myapp", Image: "fnproject/fn-test-utils", Type: "sync", Format: "http", Memory: 128, Timeout: 30, IdleTimeout: 30, Headers: map[string][]string{"X-Function": {"Test"}}},
+			{Path: "/myhotjason", AppName: "myapp", Image: "fnproject/fn-test-utils", Type: "sync", Format: "json", Memory: 128, Timeout: 30, IdleTimeout: 30, Headers: map[string][]string{"X-Function": {"Test"}}},
 			{Path: "/myroute", AppName: "myapp", Image: "fnproject/fn-test-utils", Type: "sync", Memory: 128, Timeout: 30, IdleTimeout: 30, Headers: map[string][]string{"X-Function": {"Test"}}},
 			{Path: "/myerror", AppName: "myapp", Image: "fnproject/fn-test-utils", Type: "sync", Memory: 128, Timeout: 30, IdleTimeout: 30, Headers: map[string][]string{"X-Function": {"Test"}}},
 			{Path: "/mydne", AppName: "myapp", Image: "fnproject/imagethatdoesnotexist", Type: "sync", Memory: 128, Timeout: 30, IdleTimeout: 30},
@@ -152,6 +153,7 @@ func TestRouteRunnerExecution(t *testing.T) {
 	crasher := `{"sleepTime": 0, "isDebug": true, "isCrash": true}`          // crash container
 	oomer := `{"sleepTime": 0, "isDebug": true, "allocateMemory": 12000000}` // ask for 12MB
 	badHttp := `{"sleepTime": 0, "isDebug": true, "responseCode": -1}`       // http status of -1 (invalid http)
+	badHot := `{"invalidResponse": true, "isDebug": true}`                   // write a not json/http as output
 	ok := `{"sleepTime": 0, "isDebug": true}`                                // good response / ok
 
 	for i, test := range []struct {
@@ -164,21 +166,17 @@ func TestRouteRunnerExecution(t *testing.T) {
 	}{
 		{"/r/myapp/", ok, "GET", http.StatusOK, expHeaders, ""},
 
-		// TODO: this should return 502 and description about container misbehaving
-		{"/r/myapp/myhot", badHttp, "GET", http.StatusInternalServerError, expHeaders, "internal server error"},
+		{"/r/myapp/myhot", badHttp, "GET", http.StatusBadGateway, expHeaders, "invalid http response"},
 		// hot container now back to normal, we should get OK
 		{"/r/myapp/myhot", ok, "GET", http.StatusOK, expHeaders, ""},
 
+		{"/r/myapp/myhot", badHot, "GET", http.StatusBadGateway, expHeaders, "invalid http response"},
+		{"/r/myapp/myhotjason", badHot, "GET", http.StatusBadGateway, expHeaders, "invalid json response"},
+
 		{"/r/myapp/myroute", ok, "GET", http.StatusOK, expHeaders, ""},
 		{"/r/myapp/myerror", crasher, "GET", http.StatusBadGateway, expHeaders, "container exit code 2"},
 		{"/r/myapp/mydne", ``, "GET", http.StatusNotFound, nil, "pull access denied"},
 		{"/r/myapp/mydnehot", ``, "GET", http.StatusNotFound, nil, "pull access denied"},
-
-		// Added same tests again to check if time is reduced by the auth cache
-		{"/r/myapp/", ok, "GET", http.StatusOK, expHeaders, ""},
-		{"/r/myapp/myroute", ok, "GET", http.StatusOK, expHeaders, ""},
-		{"/r/myapp/myerror", crasher, "GET", http.StatusBadGateway, expHeaders, "container exit code 2"},
-		{"/r/myapp/myerror", crasher, "GET", http.StatusBadGateway, expHeaders, "container exit code 2"},
 		{"/r/myapp/myoom", oomer, "GET", http.StatusBadGateway, nil, "container out of memory"},
 	} {
 		body := strings.NewReader(test.body)