diff --git a/src/ytdl_sub/script/parser.py b/src/ytdl_sub/script/parser.py
index 0573380a..7c098755 100644
--- a/src/ytdl_sub/script/parser.py
+++ b/src/ytdl_sub/script/parser.py
@@ -26,6 +26,7 @@ from ytdl_sub.validators.string_formatter_validators import is_valid_source_vari
 # pylint: disable=invalid-name
 # pylint: disable=too-many-branches
 # pylint: disable=too-many-return-statements
+# pylint: disable=consider-using-ternary
 
 
 class ParsedArgType(Enum):
@@ -56,6 +57,8 @@ BOOLEAN_ONLY_ARGS = InvalidSyntaxException(
     "Booleans can only be used as arguments to functions, maps, or arrays"
 )
 
+FUNCTION_INVALID_CHAR = InvalidSyntaxException("Invalid value when parsing a function")
+
 
 def _UNEXPECTED_CHAR_ARGUMENT(arg_type: ParsedArgType):
     return InvalidSyntaxException(f"Unexpected character when parsing {arg_type.value} arguments")
@@ -79,6 +82,10 @@ def _is_variable_start(char: str) -> bool:
     return char.isalpha() and char.islower()
 
 
+def _is_function_name_char(char: str) -> bool:
+    return (char.isalpha() and char.islower()) or char.isnumeric() or char == "_"
+
+
 def _is_numeric_start(char: str) -> bool:
     return char.isnumeric() or char == "-"
 
@@ -329,12 +336,15 @@ class _Parser:
                     self._set_highlight_position(function_start_pos)
                     raise
 
-            if ch != "(":
+            if _is_function_name_char(ch):
                 function_name += ch
-            else:
+            elif ch == "(":
                 function_args = self._parse_args(argument_parser=ParsedArgType.FUNCTION)
+            else:
+                break
 
-        raise StringFormattingException("Invalid function")
+        self._set_highlight_position(pos=self._pos - 1)
+        raise FUNCTION_INVALID_CHAR
 
     def _parse_array(self) -> UnresolvedArray:
         """
diff --git a/tests/unit/script/types/test_function.py b/tests/unit/script/types/test_function.py
index 1e5f7b33..0f3e6997 100644
--- a/tests/unit/script/types/test_function.py
+++ b/tests/unit/script/types/test_function.py
@@ -2,12 +2,14 @@ import re
 
 import pytest
 
+from ytdl_sub.script.parser import FUNCTION_INVALID_CHAR
 from ytdl_sub.script.script import Script
 from ytdl_sub.script.types.resolvable import Boolean
 from ytdl_sub.script.types.resolvable import String
 from ytdl_sub.script.utils.exceptions import FunctionDoesNotExist
 from ytdl_sub.script.utils.exceptions import FunctionRuntimeException
 from ytdl_sub.script.utils.exceptions import IncompatibleFunctionArguments
+from ytdl_sub.script.utils.exceptions import InvalidSyntaxException
 from ytdl_sub.script.utils.exceptions import UserThrownRuntimeError
 
 
@@ -105,3 +107,10 @@ class TestFunction:
             match=re.escape("Function %lolnope does not exist as a built-in or custom function."),
         ):
             Script({"dne": "{%lolnope(False, 'test this error message')}"}).resolve()
+
+    def test_function_does_not_close(self):
+        with pytest.raises(
+            InvalidSyntaxException,
+            match=re.escape(str(FUNCTION_INVALID_CHAR)),
+        ):
+            Script({"dne": "{%throw}"}).resolve()