diff --git a/src/openapi_python_generator/language_converters/python/common.py b/src/openapi_python_generator/language_converters/python/common.py
index 72da991..49019a5 100644
--- a/src/openapi_python_generator/language_converters/python/common.py
+++ b/src/openapi_python_generator/language_converters/python/common.py
@@ -49,8 +49,10 @@ def normalize_symbol(symbol: str) -> str:
     :param symbol: name of the identifier
     :return: normalized identifier name
     """
-    symbol = symbol.replace("-", "_")
+    symbol = symbol.replace("-", "_").replace(" ", "_")
     normalized_symbol = _symbol_ascii_strip_re.sub("", symbol)
     if normalized_symbol in keyword.kwlist:
         normalized_symbol = normalized_symbol + "_"
+    if len(normalized_symbol) > 0 and normalized_symbol[0].isnumeric():
+        normalized_symbol = "_" + normalized_symbol
     return normalized_symbol
diff --git a/src/openapi_python_generator/language_converters/python/jinja_config.py b/src/openapi_python_generator/language_converters/python/jinja_config.py
index 172ca70..1a0704b 100644
--- a/src/openapi_python_generator/language_converters/python/jinja_config.py
+++ b/src/openapi_python_generator/language_converters/python/jinja_config.py
@@ -16,7 +16,7 @@
 
 def create_jinja_env():
     custom_template_path = common.get_custom_template_path()
-    return Environment(
+    environment = Environment(
         loader=(
             ChoiceLoader(
                 [
@@ -30,3 +30,7 @@ def create_jinja_env():
         autoescape=True,
         trim_blocks=True,
     )
+
+    environment.filters["normalize_symbol"] = common.normalize_symbol
+
+    return environment
diff --git a/src/openapi_python_generator/language_converters/python/model_generator.py b/src/openapi_python_generator/language_converters/python/model_generator.py
index 0b7943e..d494b1d 100644
--- a/src/openapi_python_generator/language_converters/python/model_generator.py
+++ b/src/openapi_python_generator/language_converters/python/model_generator.py
@@ -1,5 +1,4 @@
 import itertools
-import re
 from typing import List, Optional, Union
 
 import click
@@ -414,10 +413,8 @@ def generate_models(
         name = common.normalize_symbol(schema_name)
         if schema_or_reference.enum is not None:
             value_dict = schema_or_reference.model_dump()
-            regex = re.compile(r"[\s\/=\*\+]+")
             value_dict["enum"] = [
-                re.sub(regex, "_", i) if isinstance(i, str) else f"value_{i}"
-                for i in value_dict["enum"]
+                (common.normalize_symbol(str(i)).upper(), i) for i in value_dict["enum"]
             ]
             m = Model(
                 file_name=name,
diff --git a/src/openapi_python_generator/language_converters/python/templates/enum.jinja2 b/src/openapi_python_generator/language_converters/python/templates/enum.jinja2
index f88bdd6..848f159 100644
--- a/src/openapi_python_generator/language_converters/python/templates/enum.jinja2
+++ b/src/openapi_python_generator/language_converters/python/templates/enum.jinja2
@@ -1,9 +1,11 @@
 from enum import Enum
 
 class {{ name }}(str, Enum):
-    {% for enumItem in enum %}
+    {% for enumItemIdent, enumItem in enum %}
 
     {% if enumItem is string %}
-    {{ enumItem.upper() }} = '{{ enumItem }}'{% else %}
-    value_{{ enumItem }} = {{ enumItem }}{% endif %}
+    {{ enumItemIdent }} = '{{ enumItem }}'
+    {% else %}
+    {{ enumItemIdent }} = {{ enumItem }}
+    {% endif %}
     {% endfor %}
diff --git a/src/openapi_python_generator/language_converters/python/templates/models.jinja2 b/src/openapi_python_generator/language_converters/python/templates/models.jinja2
index fbf2e4e..3ff37e4 100644
--- a/src/openapi_python_generator/language_converters/python/templates/models.jinja2
+++ b/src/openapi_python_generator/language_converters/python/templates/models.jinja2
@@ -20,5 +20,5 @@ class {{ schema_name }}(BaseModel):
     """
     {% for property in properties %}
 
-    {{ property.name | replace("@","") | replace("-","_") }} : {{ property.type.converted_type | safe }} = Field(alias="{{ property.name }}" {% if not property.required %}, default = {{ property.default }} {% endif %})
+    {{ property.name | normalize_symbol }} : {{ property.type.converted_type | safe }} = Field(alias="{{ property.name }}" {% if not property.required %}, default = {{ property.default }} {% endif %})
     {% endfor %}
diff --git a/src/openapi_python_generator/language_converters/python/templates/models_pydantic_2.jinja2 b/src/openapi_python_generator/language_converters/python/templates/models_pydantic_2.jinja2
index 36edd3b..99bdfcd 100644
--- a/src/openapi_python_generator/language_converters/python/templates/models_pydantic_2.jinja2
+++ b/src/openapi_python_generator/language_converters/python/templates/models_pydantic_2.jinja2
@@ -24,5 +24,5 @@ class {{ schema_name }}(BaseModel):
     }
     {% for property in properties %}
 
-    {{ property.name | replace("@","") | replace("-","_") }} : {{ property.type.converted_type | safe }} = Field(validation_alias="{{ property.name }}" {% if not property.required %}, default = {{ property.default }} {% endif %})
-    {% endfor %}
\ No newline at end of file
+    {{ property.name | normalize_symbol }} : {{ property.type.converted_type | safe }} = Field(validation_alias="{{ property.name }}" {% if not property.required %}, default = {{ property.default }} {% endif %})
+    {% endfor %}
diff --git a/tests/regression/test_issue_30_87.py b/tests/regression/test_issue_30_87.py
new file mode 100644
index 0000000..7456f2f
--- /dev/null
+++ b/tests/regression/test_issue_30_87.py
@@ -0,0 +1,24 @@
+import pytest
+
+from openapi_python_generator.common import HTTPLibrary
+from openapi_python_generator.generate_data import get_open_api
+from openapi_python_generator.parsers import generate_code_3_1
+from tests.conftest import test_data_folder
+
+
+@pytest.mark.parametrize(
+    "library",
+    [HTTPLibrary.httpx, HTTPLibrary.aiohttp, HTTPLibrary.requests],
+)
+def test_issue_30_87(library) -> None:
+    """
+    https://github.com/MarcoMuellner/openapi-python-generator/issues/30
+    https://github.com/MarcoMuellner/openapi-python-generator/issues/87
+    """
+    openapi_obj, version = get_open_api(str(test_data_folder / "issue_30_87.json"))
+    result = generate_code_3_1(openapi_obj, library)  # type: ignore
+
+    expected_model = [m for m in result.models if m.openapi_object.title == "UserType"][
+        0
+    ]
+    assert "ADMIN_USER = 'admin-user'" in expected_model.content
diff --git a/tests/regression/test_issue_55.py b/tests/regression/test_issue_55.py
new file mode 100644
index 0000000..572d610
--- /dev/null
+++ b/tests/regression/test_issue_55.py
@@ -0,0 +1,23 @@
+import pytest
+
+from openapi_python_generator.common import HTTPLibrary
+from openapi_python_generator.generate_data import get_open_api
+from openapi_python_generator.parsers import generate_code_3_1
+from tests.conftest import test_data_folder
+
+
+@pytest.mark.parametrize(
+    "library",
+    [HTTPLibrary.httpx, HTTPLibrary.aiohttp, HTTPLibrary.requests],
+)
+def test_issue_55(library) -> None:
+    """
+    https://github.com/MarcoMuellner/openapi-python-generator/issues/55
+    """
+    openapi_obj, version = get_open_api(str(test_data_folder / "issue_55.json"))
+    result = generate_code_3_1(openapi_obj, library)  # type: ignore
+
+    expected_model = [m for m in result.models if m.openapi_object.title == "UserType"][
+        0
+    ]
+    assert "ADMIN_USER = 'admin user'" in expected_model.content
diff --git a/tests/test_data/issue_30_87.json b/tests/test_data/issue_30_87.json
new file mode 100644
index 0000000..4f4f15a
--- /dev/null
+++ b/tests/test_data/issue_30_87.json
@@ -0,0 +1,70 @@
+{
+  "openapi": "3.0.2",
+  "info": {
+    "title": "Title",
+    "version": "1.0"
+  },
+  "paths": {
+    "/users": {
+      "get": {
+        "summary": "Get users",
+        "description": "Returns a list of users.",
+        "operationId": "users_get",
+        "parameters": [
+          {
+            "name": "type",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "$ref": "#/components/schemas/UserType"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Successful response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/User"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "UserType": {
+        "title": "UserType",
+        "description": "An enumeration.",
+        "enum": ["admin-user", "regular-user"]
+      },
+      "User": {
+        "title": "User",
+        "description": "A user.",
+        "type": "object",
+        "properties": {
+          "id": {
+            "type": "string",
+            "format": "uuid"
+          },
+          "name": {
+            "type": "string"
+          },
+          "type": {
+            "$ref": "#/components/schemas/UserType"
+          },
+          "30d_active": {
+            "type": "boolean"
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/tests/test_data/issue_55.json b/tests/test_data/issue_55.json
new file mode 100644
index 0000000..3de3259
--- /dev/null
+++ b/tests/test_data/issue_55.json
@@ -0,0 +1,70 @@
+{
+  "openapi": "3.0.2",
+  "info": {
+    "title": "Title",
+    "version": "1.0"
+  },
+  "paths": {
+    "/users": {
+      "get": {
+        "summary": "Get users",
+        "description": "Returns a list of users.",
+        "operationId": "users_get",
+        "parameters": [
+          {
+            "name": "type",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "$ref": "#/components/schemas/UserType"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Successful response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/User"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "UserType": {
+        "title": "UserType",
+        "description": "An enumeration.",
+        "enum": ["admin user", "regular user"]
+      },
+      "User": {
+        "title": "User",
+        "description": "A user.",
+        "type": "object",
+        "properties": {
+          "id": {
+            "type": "string",
+            "format": "uuid"
+          },
+          "name": {
+            "type": "string"
+          },
+          "type": {
+            "$ref": "#/components/schemas/UserType"
+          },
+          "30d_active": {
+            "type": "boolean"
+          }
+        }
+      }
+    }
+  }
+}