diff --git a/scapy/layers/ntp.py b/scapy/layers/ntp.py
index f8dbe16b4..5941ad4ce 100644
--- a/scapy/layers/ntp.py
+++ b/scapy/layers/ntp.py
@@ -214,7 +214,7 @@ class NTP(Packet):
         if cls == "NTP":
             if isinstance(self, NTP):
                 return True
-        elif issubclass(cls, NTP):
+        elif not isinstance(cls, str) and issubclass(cls, NTP):
             if isinstance(self, cls):
                 return True
         return super(NTP, self).haslayer(cls)
diff --git a/test/regression.uts b/test/regression.uts
index 66e62ec6f..c0b934161 100644
--- a/test/regression.uts
+++ b/test/regression.uts
@@ -7053,7 +7053,6 @@ assert(not NTPControl in p)
 assert(NTPPrivate in p)
 assert(NTP in p)
 
-
 = NTP - Layers (2)
 p = NTPHeader()
 assert(type(p[NTP]) == NTPHeader)
@@ -7062,6 +7061,17 @@ assert(type(p[NTP]) == NTPControl)
 p = NTPPrivate()
 assert(type(p[NTP]) == NTPPrivate)
 
+= NTP - sessions (1)
+p = IP()/TCP()/NTP()
+l = PacketList(p)
+s = l.sessions()  # Crashed on commit: e42ecdc54556c4852ca06b1a6da6c1ccbf3f522e
+assert len(s) == 1
+
+= NTP - sessions (2)
+p = IP()/UDP()/NTP()
+l = PacketList(p)
+s = l.sessions()  # Crashed on commit: e42ecdc54556c4852ca06b1a6da6c1ccbf3f522e
+assert len(s) == 1
 
 ############
 ############