diff --git a/src/libstore-c/nix_api_store.cc b/src/libstore-c/nix_api_store.cc
index aa4ab521a..6ce4d01bb 100644
--- a/src/libstore-c/nix_api_store.cc
+++ b/src/libstore-c/nix_api_store.cc
@@ -56,11 +56,7 @@ void nix_store_free(Store * store)
     delete store;
 }
 
-nix_err nix_store_get_uri(
-    nix_c_context * context,
-    Store * store,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data)
+nix_err nix_store_get_uri(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -71,11 +67,8 @@ nix_err nix_store_get_uri(
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_store_get_version(
-    nix_c_context * context,
-    Store * store,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data)
+nix_err
+nix_store_get_version(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -136,13 +129,10 @@ nix_err nix_store_realise(
     NIXC_CATCH_ERRS
 }
 
-void nix_store_path_name(
-    const StorePath * store_path,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data)
+void nix_store_path_name(const StorePath * store_path, nix_get_string_callback callback, void * user_data)
 {
     std::string_view name = store_path->path.name();
-    ((nix_get_string_callback) callback)(name.data(), name.size(), user_data);
+    callback(name.data(), name.size(), user_data);
 }
 
 void nix_store_path_free(StorePath * sp)
diff --git a/src/libstore-c/nix_api_store.h b/src/libstore-c/nix_api_store.h
index efeedbf7b..c83aca3f7 100644
--- a/src/libstore-c/nix_api_store.h
+++ b/src/libstore-c/nix_api_store.h
@@ -76,11 +76,7 @@ void nix_store_free(Store * store);
  * @see nix_get_string_callback
  * @return error code, NIX_OK on success.
  */
-nix_err nix_store_get_uri(
-    nix_c_context * context,
-    Store * store,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data);
+nix_err nix_store_get_uri(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data);
 
 // returns: owned StorePath*
 /**
@@ -101,10 +97,7 @@ StorePath * nix_store_parse_path(nix_c_context * context, Store * store, const c
  * @param[in] callback called with the name
  * @param[in] user_data arbitrary data, passed to the callback when it's called.
  */
-void nix_store_path_name(
-    const StorePath * store_path,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data);
+void nix_store_path_name(const StorePath * store_path, nix_get_string_callback callback, void * user_data);
 
 /**
  * @brief Copy a StorePath
@@ -163,11 +156,8 @@ nix_err nix_store_realise(
  * @see nix_get_string_callback
  * @return error code, NIX_OK on success.
  */
-nix_err nix_store_get_version(
-    nix_c_context * context,
-    Store * store,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data);
+nix_err
+nix_store_get_version(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data);
 
 // cffi end
 #ifdef __cplusplus
diff --git a/src/libutil-c/nix_api_util.cc b/src/libutil-c/nix_api_util.cc
index 4999e28e9..0a9b49345 100644
--- a/src/libutil-c/nix_api_util.cc
+++ b/src/libutil-c/nix_api_util.cc
@@ -64,11 +64,7 @@ const char * nix_version_get()
 
 // Implementations
 
-nix_err nix_setting_get(
-    nix_c_context * context,
-    const char * key,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data)
+nix_err nix_setting_get(nix_c_context * context, const char * key, nix_get_string_callback callback, void * user_data)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -120,10 +116,7 @@ const char * nix_err_msg(nix_c_context * context, const nix_c_context * read_con
 }
 
 nix_err nix_err_name(
-    nix_c_context * context,
-    const nix_c_context * read_context,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data)
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -134,10 +127,7 @@ nix_err nix_err_name(
 }
 
 nix_err nix_err_info_msg(
-    nix_c_context * context,
-    const nix_c_context * read_context,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data)
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -153,9 +143,8 @@ nix_err nix_err_code(const nix_c_context * read_context)
 }
 
 // internal
-nix_err call_nix_get_string_callback(
-    const std::string str, void (*callback)(const char * start, unsigned int n, void * user_data), void * user_data)
+nix_err call_nix_get_string_callback(const std::string str, nix_get_string_callback callback, void * user_data)
 {
-    ((nix_get_string_callback) callback)(str.c_str(), str.size(), user_data);
+    callback(str.c_str(), str.size(), user_data);
     return NIX_OK;
 }
diff --git a/src/libutil-c/nix_api_util.h b/src/libutil-c/nix_api_util.h
index 36a3f76cb..e0ca04e69 100644
--- a/src/libutil-c/nix_api_util.h
+++ b/src/libutil-c/nix_api_util.h
@@ -175,11 +175,7 @@ nix_err nix_libutil_init(nix_c_context * context);
  * @return NIX_ERR_KEY if the setting is unknown, or NIX_OK if the setting was retrieved
  * successfully.
  */
-nix_err nix_setting_get(
-    nix_c_context * context,
-    const char * key,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data);
+nix_err nix_setting_get(nix_c_context * context, const char * key, nix_get_string_callback callback, void * user_data);
 
 /**
  * @brief Sets a setting in the nix global configuration.
@@ -246,10 +242,7 @@ const char * nix_err_msg(nix_c_context * context, const nix_c_context * ctx, uns
  * @return NIX_OK if there were no errors, an error code otherwise.
  */
 nix_err nix_err_info_msg(
-    nix_c_context * context,
-    const nix_c_context * read_context,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data);
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data);
 
 /**
  * @brief Retrieves the error name from a context.
@@ -268,10 +261,7 @@ nix_err nix_err_info_msg(
  * @return NIX_OK if there were no errors, an error code otherwise.
  */
 nix_err nix_err_name(
-    nix_c_context * context,
-    const nix_c_context * read_context,
-    void (*callback)(const char * start, unsigned int n, void * user_data),
-    void * user_data);
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data);
 
 /**
  * @brief Retrieves the most recent error code from a nix_c_context
diff --git a/src/libutil-c/nix_api_util_internal.h b/src/libutil-c/nix_api_util_internal.h
index fe5d5db18..aa829feaf 100644
--- a/src/libutil-c/nix_api_util_internal.h
+++ b/src/libutil-c/nix_api_util_internal.h
@@ -29,8 +29,7 @@ nix_err nix_context_error(nix_c_context * context);
  * @return NIX_OK if there were no errors.
  * @see nix_get_string_callback
  */
-nix_err call_nix_get_string_callback(
-    const std::string str, void (*callback)(const char * start, unsigned int n, void * user_data), void * user_data);
+nix_err call_nix_get_string_callback(const std::string str, nix_get_string_callback callback, void * user_data);
 
 #define NIXC_CATCH_ERRS \
     catch (...) \
diff --git a/tests/unit/libutil-support/tests/string_callback.hh b/tests/unit/libutil-support/tests/string_callback.hh
index 6420810b6..3a3e545e9 100644
--- a/tests/unit/libutil-support/tests/string_callback.hh
+++ b/tests/unit/libutil-support/tests/string_callback.hh
@@ -11,7 +11,6 @@ inline void * observe_string_cb_data(std::string & out)
 };
 
 #define OBSERVE_STRING(str) \
-    (void (*)(const char *, unsigned int, void *)) nix::testing::observe_string_cb, \
-        nix::testing::observe_string_cb_data(str)
+  (nix_get_string_callback) nix::testing::observe_string_cb, nix::testing::observe_string_cb_data(str)
 
 }