diff --git a/interfaces/cython/cantera/ck2cti.py b/interfaces/cython/cantera/ck2cti.py
index 33085eaef..8d1182e01 100644
--- a/interfaces/cython/cantera/ck2cti.py
+++ b/interfaces/cython/cantera/ck2cti.py
@@ -1564,7 +1564,7 @@ class Parser(object):
                 if tokens[0].upper().startswith('ELEM'):
                     inHeader = False
                     tokens = tokens[1:]
-                    while line is not None and not contains(line, 'END'):
+                    while line is not None and get_index(line, 'END') is None:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('SPEC', 'SPECIES'):
@@ -1588,7 +1588,7 @@ class Parser(object):
                     # List of species identifiers
                     tokens = tokens[1:]
                     inHeader = False
-                    while line is not None and not contains(line, 'END'):
+                    while line is not None and get_index(line, 'END') is None:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('REAC', 'REACTIONS', 'TRAN',
@@ -1638,7 +1638,7 @@ class Parser(object):
                     surf = self.surfaces[-1]
 
                     inHeader = False
-                    while line is not None and not contains(line, 'END'):
+                    while line is not None and get_index(line, 'END') is None:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('REAC', 'REACTIONS', 'THER',
@@ -1678,7 +1678,7 @@ class Parser(object):
                     inHeader = False
                     entryLength = None
                     entry = []
-                    while line is not None and not get_index(line, 'END') == 0:
+                    while line is not None and get_index(line, 'END') != 0:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('REAC', 'REACTIONS', 'TRAN', 'TRANSPORT'):
@@ -1735,11 +1735,11 @@ class Parser(object):
                     # List of thermodynamics (hopefully one per species!)
                     inHeader = False
                     line, comment = readline()
-                    if line is not None and not contains(line, 'END'):
+                    if line is not None and get_index(line, 'END') is None:
                         TintDefault = float(line.split()[1])
                     thermo = []
                     current = []
-                    while line is not None and not contains(line, 'END'):
+                    while line is not None and get_index(line, 'END') != 0:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('REAC', 'REACTIONS', 'TRAN', 'TRANSPORT'):
@@ -1831,7 +1831,7 @@ class Parser(object):
                         reactions = self.surfaces[-1].reactions
                     else:
                         reactions = self.reactions
-                    while line is not None and not contains(line, 'END'):
+                    while line is not None and get_index(line, 'END') is None:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('TRAN', 'TRANSPORT'):
@@ -1893,7 +1893,7 @@ class Parser(object):
                     inHeader = False
                     line, comment = readline()
                     transport_start_line = self.line_number
-                    while line is not None and not contains(line, 'END'):
+                    while line is not None and get_index(line, 'END') is None:
                         # Grudging support for implicit end of section
                         start = line.strip().upper().split()
                         if start and start[0] in ('REAC', 'REACTIONS'):
diff --git a/test/data/species-names.inp b/test/data/species-names.inp
index 8371af2ab..1308c9efc 100644
--- a/test/data/species-names.inp
+++ b/test/data/species-names.inp
@@ -31,7 +31,7 @@ trans_butene            C   1H   4          G   200.000  3500.000  1000.000    1
  7.48514950E-02 1.33909467E-02-5.73285809E-06 1.22292535E-09-1.01815230E-13    2
 -9.46834459E+03 1.84373180E+01 5.14987613E+00-1.36709788E-02 4.91800599E-05    3
 -4.84743026E-08 1.66693956E-11-1.02466476E+04-4.64130376E+00                   4
-plus+                   C   1H   4          G   200.000  3500.000  1000.000    1
+plus+       nottheend   C   1H   4          G   200.000  3500.000  1000.000    1
  7.48514950E-02 1.33909467E-02-5.73285809E-06 1.22292535E-09-1.01815230E-13    2
 -9.46834459E+03 1.84373180E+01 5.14987613E+00-1.36709788E-02 4.91800599E-05    3
 -4.84743026E-08 1.66693956E-11-1.02466476E+04-4.64130376E+00                   4