diff --git a/doc/libpkgconf-fragment.rst b/doc/libpkgconf-fragment.rst
index e9029e8..6a38b37 100644
--- a/doc/libpkgconf-fragment.rst
+++ b/doc/libpkgconf-fragment.rst
@@ -44,6 +44,7 @@ which is composable, mergeable and reorderable.
    :param pkgconf_list_t* dest: The destination list.
    :param pkgconf_list_t* src: The source list.
    :param pkgconf_fragment_filter_func_t filter_func: The filter function to use.
+   :param void* data: Optional data to pass to the filter function.
    :param uint flags: A set of dependency resolver flags.
    :return: nothing
 
diff --git a/libpkgconf/fragment.c b/libpkgconf/fragment.c
index c2f8a44..974d2bd 100644
--- a/libpkgconf/fragment.c
+++ b/libpkgconf/fragment.c
@@ -355,11 +355,12 @@ pkgconf_fragment_copy(pkgconf_list_t *list, const pkgconf_fragment_t *base, unsi
  *    :param pkgconf_list_t* dest: The destination list.
  *    :param pkgconf_list_t* src: The source list.
  *    :param pkgconf_fragment_filter_func_t filter_func: The filter function to use.
+ *    :param void* data: Optional data to pass to the filter function.
  *    :param uint flags: A set of dependency resolver flags.
  *    :return: nothing
  */
 void
-pkgconf_fragment_filter(const pkgconf_client_t *client, pkgconf_list_t *dest, pkgconf_list_t *src, pkgconf_fragment_filter_func_t filter_func, unsigned int flags)
+pkgconf_fragment_filter(const pkgconf_client_t *client, pkgconf_list_t *dest, pkgconf_list_t *src, pkgconf_fragment_filter_func_t filter_func, void *data, unsigned int flags)
 {
 	pkgconf_node_t *node;
 
@@ -367,7 +368,7 @@ pkgconf_fragment_filter(const pkgconf_client_t *client, pkgconf_list_t *dest, pk
 	{
 		pkgconf_fragment_t *frag = node->data;
 
-		if (filter_func(client, frag, flags))
+		if (filter_func(client, frag, data, flags))
 			pkgconf_fragment_copy(dest, frag, flags, true);
 	}
 }
diff --git a/libpkgconf/libpkgconf.h b/libpkgconf/libpkgconf.h
index f2e6abf..a59b7cd 100644
--- a/libpkgconf/libpkgconf.h
+++ b/libpkgconf/libpkgconf.h
@@ -227,13 +227,13 @@ int pkgconf_argv_split(const char *src, int *argc, char ***argv);
 void pkgconf_argv_free(char **argv);
 
 /* fragment.c */
-typedef bool (*pkgconf_fragment_filter_func_t)(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, unsigned int flags);
+typedef bool (*pkgconf_fragment_filter_func_t)(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, void *data, unsigned int flags);
 void pkgconf_fragment_parse(const pkgconf_client_t *client, pkgconf_list_t *list, pkgconf_list_t *vars, const char *value);
 void pkgconf_fragment_add(const pkgconf_client_t *client, pkgconf_list_t *list, const char *string);
 void pkgconf_fragment_copy(pkgconf_list_t *list, const pkgconf_fragment_t *base, unsigned int flags, bool is_private);
 void pkgconf_fragment_delete(pkgconf_list_t *list, pkgconf_fragment_t *node);
 void pkgconf_fragment_free(pkgconf_list_t *list);
-void pkgconf_fragment_filter(const pkgconf_client_t *client, pkgconf_list_t *dest, pkgconf_list_t *src, pkgconf_fragment_filter_func_t filter_func, unsigned int flags);
+void pkgconf_fragment_filter(const pkgconf_client_t *client, pkgconf_list_t *dest, pkgconf_list_t *src, pkgconf_fragment_filter_func_t filter_func, void *data, unsigned int flags);
 size_t pkgconf_fragment_render_len(const pkgconf_list_t *list);
 void pkgconf_fragment_render_buf(const pkgconf_list_t *list, char *buf, size_t len);
 char *pkgconf_fragment_render(const pkgconf_list_t *list);
diff --git a/main.c b/main.c
index 0bcf79c..b555a9b 100644
--- a/main.c
+++ b/main.c
@@ -101,10 +101,11 @@ print_package_entry(const pkgconf_pkg_t *entry, void *data)
 }
 
 static bool
-filter_cflags(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, unsigned int flags)
+filter_cflags(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, void *data, unsigned int flags)
 {
 	int got_flags = 0;
 	(void) client;
+	(void) data;
 	(void) flags;
 
 	if (pkgconf_fragment_has_system_dir(client, frag))
@@ -119,10 +120,11 @@ filter_cflags(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, un
 }
 
 static bool
-filter_libs(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, unsigned int flags)
+filter_libs(const pkgconf_client_t *client, const pkgconf_fragment_t *frag, void *data, unsigned int flags)
 {
 	int got_flags = 0;
 	(void) client;
+	(void) data;
 	(void) flags;
 
 	if (pkgconf_fragment_has_system_dir(client, frag))
@@ -383,7 +385,7 @@ apply_cflags(pkgconf_client_t *client, pkgconf_pkg_t *world, void *unused, int m
 	if (eflag != PKGCONF_PKG_ERRF_OK)
 		return false;
 
-	pkgconf_fragment_filter(client, &filtered_list, &unfiltered_list, filter_cflags, flags);
+	pkgconf_fragment_filter(client, &filtered_list, &unfiltered_list, filter_cflags, NULL, flags);
 
 	if (filtered_list.head == NULL)
 		return true;
@@ -411,7 +413,7 @@ apply_libs(pkgconf_client_t *client, pkgconf_pkg_t *world, void *unused, int max
 	if (eflag != PKGCONF_PKG_ERRF_OK)
 		return false;
 
-	pkgconf_fragment_filter(client, &filtered_list, &unfiltered_list, filter_libs, flags);
+	pkgconf_fragment_filter(client, &filtered_list, &unfiltered_list, filter_libs, NULL, flags);
 
 	if (filtered_list.head == NULL)
 		return true;