diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 3e5cefa..f368455 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,5 +1,6 @@
 set(CMAKE_Fortran_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/src/mod_files)
-add_library(yajl_fort yajl_fort.F90 f90_assert.F90)
+include_directories(${YAJL_INCLUDE_DIR})
+add_library(yajl_fort yajl_fort.F90 yajl_ext.c f90_assert.F90)
 install(TARGETS yajl_fort DESTINATION lib)
 target_link_libraries(yajl_fort ${LIBS})
 
diff --git a/src/yajl_ext.c b/src/yajl_ext.c
new file mode 100644
index 0000000..122431e
--- /dev/null
+++ b/src/yajl_ext.c
@@ -0,0 +1,13 @@
+/* Fortran interoperable interfaces to the varargs function yajl_config */
+
+#include "yajl/yajl_parse.h"
+
+int yajl_set_option(yajl_handle h, yajl_option opt)
+{
+  return yajl_config(h, opt, 1);
+}
+
+int yajl_unset_option(yajl_handle h, yajl_option opt)
+{
+  return yajl_config(h, opt, 0);
+}
diff --git a/src/yajl_fort.F90 b/src/yajl_fort.F90
index 471a331..e17e23f 100644
--- a/src/yajl_fort.F90
+++ b/src/yajl_fort.F90
@@ -223,12 +223,15 @@ subroutine yajl_free(handle) bind(c)
       use,intrinsic :: iso_c_binding
       type(c_ptr), value :: handle
       end subroutine
-    function yajl_config (handle, option, enable) result(stat) bind(c)
-      use,intrinsic :: iso_c_binding
-      type(c_ptr), value :: handle
-      integer(c_int), value :: option, enable
-      integer(c_int) :: stat
-      end function
+    !yajl_config is a varargs function, and this 'single argument' declaration
+    !has been found to be non-portable.  See the 'extra' interfaces below for
+    !the replacement.
+    !function yajl_config (handle, option, enable) result(stat) bind(c)
+    !  use,intrinsic :: iso_c_binding
+    !  type(c_ptr), value :: handle
+    !  integer(c_int), value :: option, enable
+    !  integer(c_int) :: stat
+    !  end function
     function yajl_parse (handle, buffer, length) result(stat) bind(c)
       use,intrinsic :: iso_c_binding
       type(c_ptr), value :: handle
@@ -266,6 +269,22 @@ subroutine yajl_free_error(handle, str) bind(c)
       end subroutine
   end interface
 
+  !! INTEROPERABLE INTERFACES TO EXTRA YAJL C FUNCTIONS (yajl_ext.c)
+  interface
+    function yajl_set_option (handle, option) result(stat) bind(c)
+      use,intrinsic :: iso_c_binding
+      type(c_ptr), value :: handle
+      integer(c_int), value :: option
+      integer(c_int) :: stat
+      end function
+    function yajl_unset_option (handle, option) result(stat) bind(c)
+      use,intrinsic :: iso_c_binding
+      type(c_ptr), value :: handle
+      integer(c_int), value :: option
+      integer(c_int) :: stat
+      end function
+  end interface
+
   !! The Fortran yajl emitter.  This holds the handle to the C yajl generator
   !! and provides bindings to the C parser functions as type-bound procedures.
   !! Note that the callback structure and callback context that are passed
@@ -438,14 +457,14 @@ subroutine set_option (this, option)
     class(fyajl_parser), intent(in) :: this
     integer(c_int), intent(in) :: option
     integer :: stat
-    stat = yajl_config(this%handle, option, 1) ! ignore return code
+    stat = yajl_set_option(this%handle, option) ! ignore return code
   end subroutine
 
   subroutine unset_option (this, option)
     class(fyajl_parser), intent(in) :: this
     integer(c_int), intent(in) :: option
     integer :: stat
-    stat = yajl_config(this%handle, option, 0) ! ignore return code
+    stat = yajl_unset_option(this%handle, option) ! ignore return code
   end subroutine
 
   subroutine parse (this, buffer, stat)