diff --git a/src/Parsers/ExpressionElementParsers.cpp b/src/Parsers/ExpressionElementParsers.cpp
index 8a76d404531..526b3aeb2bd 100644
--- a/src/Parsers/ExpressionElementParsers.cpp
+++ b/src/Parsers/ExpressionElementParsers.cpp
@@ -689,7 +689,7 @@ bool ParserFunction::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
     ++pos;
 
     /// Avoid excessive backtracking.
-    pos.putBarrier();
+    //pos.putBarrier();
 
     /// Special cases for expressions that look like functions but contain some syntax sugar:
 
diff --git a/src/Parsers/IParser.h b/src/Parsers/IParser.h
index d4ccb9604ea..4e6dbca15a6 100644
--- a/src/Parsers/IParser.h
+++ b/src/Parsers/IParser.h
@@ -59,31 +59,11 @@ public:
     {
         uint32_t depth = 0;
         uint32_t max_depth = 0;
-        TokenIterator barrier;
 
-        Pos(Tokens & tokens_, uint32_t max_depth_) : TokenIterator(tokens_), max_depth(max_depth_), barrier(tokens_)
+        Pos(Tokens & tokens_, uint32_t max_depth_) : TokenIterator(tokens_), max_depth(max_depth_)
         {
         }
 
-        Pos & operator= (const Pos & rhs)
-        {
-            static_cast<TokenIterator &>(*this) = rhs;
-            depth = rhs.depth;
-            max_depth = rhs.max_depth;
-            if (barrier < rhs.barrier)
-                barrier = rhs.barrier;
-            return *this;
-        }
-
-        Pos & operator= (Pos && rhs)
-        {
-            *this = rhs;
-            return *this;
-        }
-
-        Pos(const Pos & rhs) = default;
-        Pos(Pos && rhs) = default;
-
         ALWAYS_INLINE void increaseDepth()
         {
             ++depth;
@@ -99,19 +79,6 @@ public:
                 throw Exception("Logical error in parser: incorrect calculation of parse depth", ErrorCodes::LOGICAL_ERROR);
             --depth;
         }
-
-        /// Will set up a barrier to avoid excessive backtracking.
-        /// E.g. after keyword CAST has been parsed it does not make sense to try to parse other alternatives.
-        void putBarrier()
-        {
-            if (barrier < *this)
-                barrier = *this;
-        }
-
-        bool feasible() const
-        {
-            return barrier <= *this;
-        }
     };
 
     /** Get the text of this parser parses. */
diff --git a/src/Parsers/IParserBase.cpp b/src/Parsers/IParserBase.cpp
index 917a586c6ce..0241250926d 100644
--- a/src/Parsers/IParserBase.cpp
+++ b/src/Parsers/IParserBase.cpp
@@ -6,10 +6,6 @@ namespace DB
 
 bool IParserBase::parse(Pos & pos, ASTPtr & node, Expected & expected)
 {
-    /// Avoid excessive backtracking.
-    if (!pos.feasible())
-        return false;
-
     expected.add(pos, getName());
 
     return wrapParseImpl(pos, IncreaseDepthTag{}, [&]
diff --git a/tests/queries/0_stateless/01503_if_const_optimization.reference b/tests/queries/0_stateless/01503_if_const_optimization.reference
index e69de29bb2d..dec7d2fabd2 100644
--- a/tests/queries/0_stateless/01503_if_const_optimization.reference
+++ b/tests/queries/0_stateless/01503_if_const_optimization.reference
@@ -0,0 +1 @@
+\N
diff --git a/tests/queries/0_stateless/01503_if_const_optimization.sql b/tests/queries/0_stateless/01503_if_const_optimization.sql
index 047f6f757e8..a64be6bc80b 100644
--- a/tests/queries/0_stateless/01503_if_const_optimization.sql
+++ b/tests/queries/0_stateless/01503_if_const_optimization.sql
@@ -1 +1 @@
-SELECT if(CAST(NULL), '2.55', NULL) AS x; -- { serverError 42 }
+SELECT if(CAST(NULL AS Nullable(UInt8)), '2.55', NULL) AS x;
diff --git a/tests/queries/0_stateless/02154_parser_backtracking.sh b/tests/queries/0_stateless/02154_parser_backtracking.sh
index 458afab5325..af032008069 100755
--- a/tests/queries/0_stateless/02154_parser_backtracking.sh
+++ b/tests/queries/0_stateless/02154_parser_backtracking.sh
@@ -10,7 +10,7 @@ CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
 echo 'SELECT '"$(perl -e 'print "CAST(" x 100')"'a b c'"$(perl -e 'print ")" x 100')" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000 2>&1 | grep -cF 'Syntax error'
 echo 'SELECT '"$(perl -e 'print "CAST(" x 100')"'a, b'"$(perl -e 'print ")" x 100')" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000 2>&1 | grep -cF 'Syntax error'
 echo 'SELECT '"$(perl -e 'print "CAST(" x 100')"'a AS b'"$(perl -e 'print ")" x 100')" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000 2>&1 | grep -cF 'Syntax error'
-echo 'SELECT '"$(perl -e 'print "CAST(" x 100')"'1'"$(perl -e 'print ", 'UInt8')" x 100')" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000
+echo 'SELECT '"$(perl -e 'print "CAST(" x 100')"'1'"$(perl -e 'print ", '"'UInt8'"')" x 100')" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000
 echo 'SELECT '"$(perl -e 'print "CAST(" x 100')"'1'"$(perl -e 'print " AS UInt8)" x 100')" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000
 
 echo "SELECT fo,22222?LUTAY(SELECT(NOT CAUTAY(SELECT(NOT CAST(NOTT(NOT CAST(NOT NOT LEfT(NOT coARRAYlumnsFLuTAY(SELECT(NO0?LUTAY(SELECT(NOT CAUTAY(SELECT(NOT CAST(NOTT(NOT CAST(NOT NOT LEfT(NOT coARRAYlumnsFLuTAY(SELECT(NOTAYTAY(SELECT(NOTAYEFAULT(fo,22222?LUTAY(%SELECT(NOT CAST(NOT NOTAYTAY(SELECT(NOTAYEFAULT(fo,22222?LUTAY(SELECT(NOT CAST(NOT NOT (NOe)))))))))))))))))))))))))))))))))" | ${CLICKHOUSE_LOCAL} --max_parser_depth 10000 2>&1 | grep -cF 'Syntax error'