diff --git a/pynest/nest/server/hl_api_server.py b/pynest/nest/server/hl_api_server.py
index ff0bd2f361..eb75763757 100644
--- a/pynest/nest/server/hl_api_server.py
+++ b/pynest/nest/server/hl_api_server.py
@@ -36,8 +36,7 @@
 from flask import Flask, jsonify, request
 from flask.logging import default_handler
 from flask_cors import CORS
-from werkzeug.exceptions import abort
-from werkzeug.wrappers import Response
+from nest.lib.hl_api_exceptions import NESTError
 
 # This ensures that the logging information shows up in the console running the server,
 # even when Flask's event loop is running.
@@ -189,41 +188,36 @@ def index():
 
 
 def do_exec(args, kwargs):
-    try:
-        source_code = kwargs.get("source", "")
-        source_cleaned = clean_code(source_code)
-
-        locals_ = dict()
-        response = dict()
-        if RESTRICTION_DISABLED:
-            with Capturing() as stdout:
-                globals_ = globals().copy()
-                globals_.update(get_modules_from_env())
-                exec(source_cleaned, globals_, locals_)
-            if len(stdout) > 0:
-                response["stdout"] = "\n".join(stdout)
-        else:
-            code = RestrictedPython.compile_restricted(source_cleaned, "<inline>", "exec")  # noqa
-            globals_ = get_restricted_globals()
+    source_code = kwargs.get("source", "")
+    source_cleaned = clean_code(source_code)
+
+    locals_ = dict()
+    response = dict()
+    if RESTRICTION_DISABLED:
+        with Capturing() as stdout:
+            globals_ = globals().copy()
             globals_.update(get_modules_from_env())
-            exec(code, globals_, locals_)
-            if "_print" in locals_:
-                response["stdout"] = "".join(locals_["_print"].txt)
-
-        if "return" in kwargs:
-            if isinstance(kwargs["return"], list):
-                data = dict()
-                for variable in kwargs["return"]:
-                    data[variable] = locals_.get(variable, None)
-            else:
-                data = locals_.get(kwargs["return"], None)
-            response["data"] = nest.serialize_data(data)
-        return response
+            get_or_error(exec)(source_cleaned, globals_, locals_)
+        if len(stdout) > 0:
+            response["stdout"] = "\n".join(stdout)
+    else:
+        code = RestrictedPython.compile_restricted(source_cleaned, "<inline>", "exec")  # noqa
+        globals_ = get_restricted_globals()
+        globals_.update(get_modules_from_env())
+        get_or_error(exec)(code, globals_, locals_)
+        if "_print" in locals_:
+            response["stdout"] = "".join(locals_["_print"].txt)
+
+    if "return" in kwargs:
+        if isinstance(kwargs["return"], list):
+            data = dict()
+            for variable in kwargs["return"]:
+                data[variable] = locals_.get(variable, None)
+        else:
+            data = locals_.get(kwargs["return"], None)
 
-    except Exception as e:
-        for line in traceback.format_exception(*sys.exc_info()):
-            print(line, flush=True)
-        flask.abort(EXCEPTION_ERROR_STATUS, str(e))
+            response["data"] = get_or_error(nest.serialize_data)(data)
+    return response
 
 
 def log(call_name, msg):
@@ -336,10 +330,43 @@ def __exit__(self, *args):
         sys.stdout = self._stdout
 
 
+class ErrorHandler(Exception):
+    status_code = 400
+    lineno = -1
+
+    def __init__(self, message: str, lineno: int = None, status_code: int = None, payload=None):
+        super().__init__()
+        self.message = message
+        if status_code is not None:
+            self.status_code = status_code
+        if lineno is not None:
+            self.lineno = lineno
+        self.payload = payload
+
+    def to_dict(self):
+        rv = dict(self.payload or ())
+        rv["message"] = self.message
+        if self.lineno != -1:
+            rv["lineNumber"] = self.lineno
+        return rv
+
+
+# https://flask.palletsprojects.com/en/2.3.x/errorhandling/
+@app.errorhandler(ErrorHandler)
+def error_handler(e):
+    return jsonify(e.to_dict()), e.status_code
+
+
+# It comments lines starting with 'import' or 'from' otherwise the line number of error would be wrong.
 def clean_code(source):
     codes = source.split("\n")
-    code_cleaned = filter(lambda code: not (code.startswith("import") or code.startswith("from")), codes)  # noqa
-    return "\n".join(code_cleaned)
+    codes_cleaned = []  # noqa
+    for code in codes:
+        if code.startswith("import") or code.startswith("from"):
+            codes_cleaned.append("#" + code)
+        else:
+            codes_cleaned.append(code)
+    return "\n".join(codes_cleaned)
 
 
 def get_arguments(request):
@@ -368,6 +395,16 @@ def get_arguments(request):
     return list(args), kwargs
 
 
+def get_lineno(err, tb_idx):
+    lineno = -1
+    if hasattr(err, "lineno") and err.lineno is not None:
+        lineno = err.lineno
+    else:
+        tb = sys.exc_info()[2]
+        lineno = traceback.extract_tb(tb)[tb_idx][1]
+    return lineno
+
+
 def get_modules_from_env():
     """Get modules from environment variable NEST_SERVER_MODULES.
 
@@ -397,13 +434,34 @@ def get_modules_from_env():
 def get_or_error(func):
     """Wrapper to get data and status."""
 
-    def func_wrapper(call, args, kwargs):
+    def func_wrapper(call, *args, **kwargs):
         try:
-            return func(call, args, kwargs)
-        except Exception as e:
-            for line in traceback.format_exception(*sys.exc_info()):
-                print(line, flush=True)
-            flask.abort(EXCEPTION_ERROR_STATUS, str(e))
+            return func(call, *args, **kwargs)
+
+        except NESTError as err:
+            error_class = err.errorname + " (NESTError)"
+            detail = err.errormessage
+            lineno = get_lineno(err, 1)
+
+        except (KeyError, SyntaxError, TypeError, ValueError) as err:
+            error_class = err.__class__.__name__
+            detail = err.args[0]
+            lineno = get_lineno(err, 1)
+
+        except Exception as err:
+            error_class = err.__class__.__name__
+            detail = err.args[0]
+            lineno = get_lineno(err, -1)
+
+        for line in traceback.format_exception(*sys.exc_info()):
+            print(line, flush=True)
+
+        if lineno == -1:
+            message = "%s: %s" % (error_class, detail)
+        else:
+            message = "%s at line %d: %s" % (error_class, lineno, detail)
+
+        raise ErrorHandler(message, lineno)
 
     return func_wrapper