diff --git a/core/action.go b/core/action.go
index 332593c..64728a2 100644
--- a/core/action.go
+++ b/core/action.go
@@ -92,7 +92,7 @@ func readStdout(stdout io.ReadCloser, source string, items chan Item, cparse cha
 	for scanout.Scan() {
 		data := scanout.Bytes()
 		err := json.Unmarshal(data, &item)
-		if err != nil {
+		if err != nil || item.Id == "" {
 			log.Printf("[%s: stdout] %s\n", source, strings.TrimSpace(string(data)))
 			parseError = true
 		} else {
diff --git a/core/action_test.go b/core/action_test.go
index a4fe599..803a3c3 100644
--- a/core/action_test.go
+++ b/core/action_test.go
@@ -71,57 +71,30 @@ func TestExecute(t *testing.T) {
 			t.Fatal("expected err")
 		}
 	}
+	execute := func(argv []string) ([]Item, error) {
+		return Execute("", argv, nil, "", time.Minute)
+	}
 
-	res, err := Execute(
-		"",
-		[]string{"true"},
-		nil,
-		"",
-		time.Minute,
-	)
+	res, err := execute([]string{"true"})
 	assertNil(err)
 	assertLen(res, 0)
 
 	// Exit with error code
-	res, err = Execute(
-		"",
-		[]string{"false"},
-		nil,
-		"",
-		time.Minute,
-	)
+	res, err = execute([]string{"false"})
 	assertNotNil(err)
 	assertLen(res, 0)
 
-	res, err = Execute(
-		"",
-		[]string{"sh", "-c", "exit 22"},
-		nil,
-		"",
-		time.Minute,
-	)
+	res, err = execute([]string{"sh", "-c", "exit 22"})
 	assertNotNil(err)
 	assertLen(res, 0)
 
 	// Timeout
-	res, err = Execute(
-		"",
-		[]string{"sleep", "10"},
-		nil,
-		"",
-		time.Millisecond,
-	)
+	res, err = Execute("", []string{"sleep", "10"}, nil, "", time.Millisecond)
 	assertNotNil(err)
 	assertLen(res, 0)
 
 	// Returning items
-	res, err = Execute(
-		"",
-		[]string{"jq", "-cn", `{id: "foo"}`},
-		nil,
-		"",
-		time.Minute,
-	)
+	res, err = execute([]string{"jq", "-cn", `{id: "foo"}`})
 	assertNil(err)
 	assertLen(res, 1)
 	if res[0].Id != "foo" {
@@ -129,13 +102,7 @@ func TestExecute(t *testing.T) {
 	}
 
 	// Read from stdin
-	res, err = Execute(
-		"",
-		[]string{"jq", "-cR", `{id: .}`},
-		nil,
-		"bar",
-		time.Minute,
-	)
+	res, err = Execute("", []string{"jq", "-cR", `{id: .}`}, nil, "bar", time.Minute)
 	assertNil(err)
 	assertLen(res, 1)
 	if res[0].Id != "bar" {
@@ -143,13 +110,7 @@ func TestExecute(t *testing.T) {
 	}
 
 	// Set env
-	res, err = Execute(
-		"",
-		[]string{"jq", "-cn", `{id: env.HELLO}`},
-		[]string{"HELLO=baz"},
-		"",
-		time.Minute,
-	)
+	res, err = Execute("", []string{"jq", "-cn", `{id: env.HELLO}`}, []string{"HELLO=baz"}, "", time.Minute)
 	assertNil(err)
 	assertLen(res, 1)
 	if res[0].Id != "baz" {
@@ -157,16 +118,33 @@ func TestExecute(t *testing.T) {
 	}
 
 	// With logging on stderr
-	res, err = Execute(
-		"",
-		[]string{"sh", "-c", `echo 1>&2 Hello; jq -cn '{id: "box"}'; echo 1>&2 World`},
-		nil,
-		"",
-		time.Minute,
-	)
+	res, err = execute([]string{"sh", "-c", `echo 1>&2 Hello; jq -cn '{id: "box"}'; echo 1>&2 World`})
 	assertNil(err)
 	assertLen(res, 1)
 	if res[0].Id != "box" {
 		t.Fatal("stderr test failed")
 	}
+
+	// Unsupported item field is silently discarded
+	res, err = execute([]string{"jq", "-cn", `{id: "test", unknownField: "what is this"}`})
+	assertNil(err)
+	assertLen(res, 1)
+
+	// Field with incorrect type fails
+	res, err = execute([]string{"jq", "-cn", `{id: ["list"]}`})
+	assertNotNil(err)
+	assertLen(res, 0)
+
+	res, err = execute([]string{"jq", "-cn", `{id: "test", time: "0"}`})
+	assertNotNil(err)
+	assertLen(res, 0)
+
+	res, err = execute([]string{"jq", "-cn", `{id: null}`})
+	assertNotNil(err)
+	assertLen(res, 0)
+
+	// Items with duplicate ids is not a fetch error, but it will fail to update
+	res, err = execute([]string{"jq", "-cn", `["a", "a"] | .[] | {id: .}`})
+	assertNil(err)
+	assertLen(res, 2)
 }