diff --git a/docs/source/capi/index.rst b/docs/source/capi/index.rst
index d7da3261e1..85e5c8ced3 100644
--- a/docs/source/capi/index.rst
+++ b/docs/source/capi/index.rst
@@ -465,13 +465,15 @@ Functions
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_statepoint_write(const char filename[])
+.. c:function:: int openmc_statepoint_write(const char filename[], const bool* write_source)
 
    Write a statepoint file
 
    :param filename: Name of file to create. If a null pointer is passed, a
                     filename is assigned automatically.
    :type filename: const char[]
+   :param write_source: Whether to include the source bank
+   :type write_source: const bool*
    :return: Return status (negative if an error occurs)
    :rtype: int
 
diff --git a/openmc/capi/core.py b/openmc/capi/core.py
index 5be31ce865..bedde6e162 100644
--- a/openmc/capi/core.py
+++ b/openmc/capi/core.py
@@ -52,7 +52,7 @@ _dll.openmc_simulation_init.restype = c_int
 _dll.openmc_simulation_init.errcheck = _error_handler
 _dll.openmc_simulation_finalize.restype = c_int
 _dll.openmc_simulation_finalize.errcheck = _error_handler
-_dll.openmc_statepoint_write.argtypes = [POINTER(c_char_p), POINTER(c_bool)]
+_dll.openmc_statepoint_write.argtypes = [c_char_p, POINTER(c_bool)]
 _dll.openmc_statepoint_write.restype = c_int
 _dll.openmc_statepoint_write.errcheck = _error_handler
 
diff --git a/src/state_point.F90 b/src/state_point.F90
index 1286bb63d4..2692856dc0 100644
--- a/src/state_point.F90
+++ b/src/state_point.F90
@@ -55,7 +55,7 @@ contains
 !===============================================================================
 
   function openmc_statepoint_write(filename, write_source) result(err) bind(C)
-    type(C_PTR),     intent(in), optional :: filename
+    type(C_PTR),     value                :: filename
     logical(C_BOOL), intent(in), optional :: write_source
     integer(C_INT) :: err
 
@@ -91,7 +91,7 @@ contains
     err = 0
 
     ! Set the filename
-    if (present(filename)) then
+    if (c_associated(filename)) then
       call c_f_pointer(filename, string, [MAX_FILE_LEN])
       filename_ = to_f_string(string)
     else