diff --git a/keysparsing.go b/keysparsing.go
index 7535379..4deed81 100644
--- a/keysparsing.go
+++ b/keysparsing.go
@@ -70,6 +70,9 @@
 	if buffer.Len() > 0 {
 		groups = append(groups, buffer.String())
 	}
+	if len(groups) == 0 {
+		return nil, fmt.Errorf("empty key")
+	}
 	return groups, nil
 }
 
diff --git a/keysparsing_test.go b/keysparsing_test.go
index 2d5379f..ef7e2a5 100644
--- a/keysparsing_test.go
+++ b/keysparsing_test.go
@@ -42,3 +42,8 @@
 func TestBaseKeyPound(t *testing.T) {
 	testError(t, "hello#world", "invalid bare character: #")
 }
+
+func TestEmptyKey(t *testing.T) {
+	testError(t, "", "empty key")
+	testError(t, " ", "empty key")
+}