diff --git a/src/installer/scripts.py b/src/installer/scripts.py
index 7929817..1a0129e 100644
--- a/src/installer/scripts.py
+++ b/src/installer/scripts.py
@@ -43,6 +43,41 @@
 """
 
 
+def _is_executable_simple(executable: bytes) -> bool:
+    if b" " in executable:
+        return False
+    shebang_length = len(executable) + 3  # Prefix #! and newline after.
+    # According to distlib, Darwin can handle up to 512 characters. But I want
+    # to avoid platform sniffing to make this as platform-agnostic as possible.
+    # The "complex" script isn't that bad anyway.
+    return shebang_length <= 127
+
+
+def _build_shebang(executable: str, forlauncher: bool) -> bytes:
+    """Build a shebang line.
+
+    The non-launcher cases are taken directly from distlib's implementation,
+    which tries its best to account for command length, spaces in path, etc.
+
+    https://bitbucket.org/pypa/distlib/src/58cd5c6/distlib/scripts.py#lines-124
+    """
+    executable_bytes = executable.encode("utf-8")
+    if forlauncher:  # The launcher can just use the command as-is.
+        return b"#!" + executable_bytes
+    if _is_executable_simple(executable_bytes):
+        return b"#!" + executable_bytes
+
+    # Shebang support for an executable with a space in it is under-specified
+    # and platform-dependent, so we use a clever hack to generate a script to
+    # run in ``/bin/sh`` that should work on all reasonably modern platforms.
+    # Read the following message to understand how the hack works:
+    # https://github.com/pypa/installer/pull/4#issuecomment-623668717
+
+    quoted = shlex.quote(executable).encode("utf-8")
+    # I don't understand a lick what this is trying to do.
+    return b"#!/bin/sh\n'''exec' " + quoted + b' "$0" "$@"\n' + b"' '''"
+
+
 class InvalidScript(ValueError):
     """Raised if the user provides incorrect script section or kind."""
 
@@ -102,7 +137,7 @@ def generate(self, executable: str, kind: "LauncherKind") -> tuple[str, bytes]:
         """
         launcher = self._get_launcher_data(kind)
         executable = self._get_alternate_executable(executable, kind)
-        shebang = self._build_shebang(executable, forlauncher=bool(launcher))
+        shebang = _build_shebang(executable, forlauncher=bool(launcher))
         code = _SCRIPT_TEMPLATE.format(
             module=self.module,
             import_name=self.attr.split(".")[0],
@@ -118,37 +153,3 @@ def generate(self, executable: str, kind: "LauncherKind") -> tuple[str, bytes]:
         name = f"{self.name}.exe"
         data = launcher + shebang + b"\n" + stream.getvalue()
         return name, data
-
-    @staticmethod
-    def _is_executable_simple(executable: bytes) -> bool:
-        if b" " in executable:
-            return False
-        shebang_length = len(executable) + 3  # Prefix #! and newline after.
-        # According to distlib, Darwin can handle up to 512 characters. But I want
-        # to avoid platform sniffing to make this as platform-agnostic as possible.
-        # The "complex" script isn't that bad anyway.
-        return shebang_length <= 127
-
-    def _build_shebang(self, executable: str, forlauncher: bool) -> bytes:
-        """Build a shebang line.
-
-        The non-launcher cases are taken directly from distlib's implementation,
-        which tries its best to account for command length, spaces in path, etc.
-
-        https://bitbucket.org/pypa/distlib/src/58cd5c6/distlib/scripts.py#lines-124
-        """
-        executable_bytes = executable.encode("utf-8")
-        if forlauncher:  # The launcher can just use the command as-is.
-            return b"#!" + executable_bytes
-        if self._is_executable_simple(executable_bytes):
-            return b"#!" + executable_bytes
-
-        # Shebang support for an executable with a space in it is under-specified
-        # and platform-dependent, so we use a clever hack to generate a script to
-        # run in ``/bin/sh`` that should work on all reasonably modern platforms.
-        # Read the following message to understand how the hack works:
-        # https://github.com/pypa/installer/pull/4#issuecomment-623668717
-
-        quoted = shlex.quote(executable).encode("utf-8")
-        # I don't understand a lick what this is trying to do.
-        return b"#!/bin/sh\n'''exec' " + quoted + b' "$0" "$@"\n' + b"' '''"
diff --git a/src/installer/utils.py b/src/installer/utils.py
index 6a22631..46ee706 100644
--- a/src/installer/utils.py
+++ b/src/installer/utils.py
@@ -24,6 +24,8 @@
     cast,
 )
 
+from installer.scripts import _build_shebang
+
 if TYPE_CHECKING:
     from installer.records import RecordEntry
     from installer.scripts import LauncherKind, ScriptSection
@@ -186,7 +188,7 @@ def fix_shebang(stream: BinaryIO, interpreter: str) -> Iterator[BinaryIO]:
     if stream.read(8) == b"#!python":
         new_stream = io.BytesIO()
         # write our new shebang
-        new_stream.write(f"#!{interpreter}\n".encode())
+        new_stream.write(_build_shebang(interpreter, False) + b"\n")
         # copy the rest of the stream
         stream.seek(0)
         stream.readline()  # skip first line