diff --git a/parser/parser.cpp b/parser/parser.cpp
index 94e3f4b4..bc4d6520 100644
--- a/parser/parser.cpp
+++ b/parser/parser.cpp
@@ -91,7 +91,7 @@ struct group_pred : if_must< one< '(' >, pad< pred, blank >, one< ')' > > {};
 struct true_pred : pegtl_istring_t("truepredicate") {};
 struct false_pred : pegtl_istring_t("falsepredicate") {};
 
-struct not_pre : sor< seq< one< '!' >, star< blank > >, seq< pegtl_istring_t("not"), plus< blank > > > {};
+struct not_pre : seq< sor< one< '!' >, seq< pegtl_istring_t("not") >, star< blank > > > {};
 struct atom_pred : seq< opt< not_pre >, pad< sor< group_pred, true_pred, false_pred, comparison_pred >, blank > > {};
 
 struct and_op : sor< pad< two< '&' >, blank >, pad_plus< pegtl_istring_t("and"), blank > > {};
diff --git a/parser/test.cpp b/parser/test.cpp
index b5fb6458..636ea316 100644
--- a/parser/test.cpp
+++ b/parser/test.cpp
@@ -51,6 +51,20 @@ static std::vector<std::string> valid_queries = {
     "0 contains 0",
     "0 BeGiNsWiTh 0",
     "0 ENDSWITH 0",
+
+    // atoms/groups
+    "(0=0)",
+    "( 0=0 )",
+    "((0=0))",
+    "!0=0",
+    "! 0=0",
+    "!(0=0)",
+    "! (0=0)",
+    "NOT0=0",   // keypath NOT0
+    "not 0=0",
+    "NOT(0=0)",
+    "not (0=0)",
+    "NOT (!0=0)",
 };
 
 static std::vector<std::string> invalid_queries = {
@@ -86,6 +100,15 @@ static std::vector<std::string> invalid_queries = {
     "0 contains1",
     "endswith 0",
 
+    // atoms/groups
+    "0=0)",
+    "(0=0",
+    "(0=0))",
+    "! =0",
+    "NOTNOT(0=0)",
+    "(!!0=0)",
+    "0=0 !",
+
     "truepredicate &&",
     "truepredicate & truepredicate",
 };