diff --git a/line_profiler/_line_profiler.pyx b/line_profiler/_line_profiler.pyx
index 15defc9a..d6d65941 100644
--- a/line_profiler/_line_profiler.pyx
+++ b/line_profiler/_line_profiler.pyx
@@ -6,6 +6,7 @@ from cpython.version cimport PY_VERSION_HEX
 from libc.stdint cimport int64_t
 
 from libcpp.unordered_map cimport unordered_map
+import threading
 
 # long long int is at least 64 bytes assuming c99
 ctypedef unsigned long long int uint64
@@ -117,13 +118,14 @@ cpdef _code_replace(func, code, co_code):
     """
     Implements CodeType.replace for Python < 3.8
     """
+    code = func.__code__
     if hasattr(code, 'replace'):
         # python 3.8+
         code = func.__code__.replace(co_code=co_code)
     else:
         # python <3.8
         co = code
-        code = CodeType(co.co_argcount, co.co_kwonlyargcount,
+        code = type(code)(co.co_argcount, co.co_kwonlyargcount,
                         co.co_nlocals, co.co_stacksize, co.co_flags,
                         co_code, co.co_consts, co.co_names,
                         co.co_varnames, co.co_filename, co.co_name,
@@ -174,18 +176,19 @@ cdef class LineProfiler:
         >>> self.print_stats()
     """
     cdef unordered_map[int64, unordered_map[int64, LineTime]] _c_code_map
-    cdef unordered_map[int64, LastTime] _c_last_time
+    # Mapping between thread-id and map of LastTime
+    cdef unordered_map[int64, unordered_map[int64, LastTime]] _c_last_time
     cdef public list functions
     cdef public dict code_hash_map, dupes_map
     cdef public double timer_unit
-    cdef public long enable_count
+    cdef public object threaddata
 
     def __init__(self, *functions):
         self.functions = []
         self.code_hash_map = {}
         self.dupes_map = {}
         self.timer_unit = hpTimerUnit()
-        self.enable_count = 0
+        self.threaddata = threading.local()
 
         for func in functions:
             self.add_function(func)
@@ -229,6 +232,14 @@ cdef class LineProfiler:
 
         self.functions.append(func)
 
+    property enable_count:
+        def __get__(self):
+            if not hasattr(self.threaddata, 'enable_count'):
+                self.threaddata.enable_count = 0
+            return self.threaddata.enable_count
+        def __set__(self, value):
+            self.threaddata.enable_count = value
+
     def enable_by_count(self):
         """ Enable the profiler if it hasn't been enabled before.
         """
@@ -263,7 +274,7 @@ cdef class LineProfiler:
         
     @property
     def c_last_time(self):
-        return <dict>self._c_last_time
+        return (<dict>self._c_last_time)[threading.get_ident()]
 
     @property
     def code_map(self):
@@ -292,7 +303,7 @@ cdef class LineProfiler:
         line_profiler 4.0 no longer directly maintains last_time, but this will
         construct something similar for backwards compatibility.
         """
-        c_last_time = self.c_last_time
+        c_last_time = (<dict>self._c_last_time)[threading.get_ident()]
         code_hash_map = self.code_hash_map
         py_last_time = {}
         for code, code_hashes in code_hash_map.items():
@@ -303,7 +314,7 @@ cdef class LineProfiler:
 
 
     cpdef disable(self):
-        self._c_last_time.clear()
+        self._c_last_time[threading.get_ident()].clear()
         unset_trace()
 
     def get_stats(self):
@@ -318,8 +329,21 @@ cdef class LineProfiler:
             for entry in self.code_hash_map[code]:
                 entries += list(cmap[entry].values())
             key = label(code)
-            stats[key] = [(e["lineno"], e["nhits"], e["total_time"]) for e in entries]
-            stats[key].sort()
+
+            entries = [(e["lineno"], e["nhits"], e["total_time"]) for e in entries]
+            # If there are multiple entries for a line, this will sort them by increasing # hits
+            entries.sort()
+
+            # NOTE: v4.x may produce more than one entry per line. For example:
+            #   1:  for x in range(10):
+            #   2:      pass
+            #  will produce a 1-hit entry on line 1, and 10-hit entries on lines 1 and 2
+            #  This doesn't affect `print_stats`, because it uses the last entry for a given line (line number is
+            #  used a dict key so earlier entries are overwritten), but to keep compatability with other tools,
+            #  let's only keep the last entry for each line
+            # Remove all but the last entry for each line
+            entries = list({e[0]: e for e in entries}.values())
+            stats[key] = entries
         return LineStats(stats, self.timer_unit)
 
 @cython.boundscheck(False)
@@ -345,8 +369,9 @@ PyObject *arg):
         code_hash = compute_line_hash(block_hash, py_frame.f_lineno)
         if self._c_code_map.count(code_hash):
             time = hpTimer()
-            if self._c_last_time.count(block_hash):
-                old = self._c_last_time[block_hash]
+            ident = threading.get_ident()
+            if self._c_last_time[ident].count(block_hash):
+                old = self._c_last_time[ident][block_hash]
                 line_entries = self._c_code_map[code_hash]
                 key = old.f_lineno
                 if not line_entries.count(key):
@@ -356,12 +381,12 @@ PyObject *arg):
             if what == PyTrace_LINE:
                 # Get the time again. This way, we don't record much time wasted
                 # in this function.
-                self._c_last_time[block_hash] = LastTime(py_frame.f_lineno, hpTimer())
-            elif self._c_last_time.count(block_hash):
+                self._c_last_time[ident][block_hash] = LastTime(py_frame.f_lineno, hpTimer())
+            elif self._c_last_time[ident].count(block_hash):
                 # We are returning from a function, not executing a line. Delete
                 # the last_time record. It may have already been deleted if we
                 # are profiling a generator that is being pumped past its end.
-                self._c_last_time.erase(self._c_last_time.find(block_hash))
+                self._c_last_time[ident].erase(self._c_last_time[ident].find(block_hash))
 
     return 0