diff --git a/api.go b/api.go
index c5b8c2e..e0f46f9 100644
--- a/api.go
+++ b/api.go
@@ -151,6 +151,12 @@ func errMsg(b []byte) error {
 		return err
 	}
 
+	// if error response does not contain "message" field,
+	// return the full error JSON
+	if errResp.Message == "" {
+		return errors.New(string(b))
+	}
+
 	return errors.New(errResp.Message)
 }
 
diff --git a/api_test.go b/api_test.go
index 9c86186..730c6a2 100644
--- a/api_test.go
+++ b/api_test.go
@@ -1864,3 +1864,19 @@ func TestCRUDSiteRequestRule(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestErrMsg(t *testing.T) {
+	cases := []struct {
+		in   []byte
+		want string
+	}{
+		{[]byte(`{"message": "an error message"}`), "an error message"},
+		{[]byte(`{"detail": "an error message"}`), `{"detail": "an error message"}`},
+	}
+
+	for _, tt := range cases {
+		if err := errMsg(tt.in); err.Error() != tt.want {
+			t.Errorf("got error message = %q, want %q", err.Error(), tt.want)
+		}
+	}
+}