diff --git a/include/qapi/error.h b/include/qapi/error.h
index 34af4e103f..692e01346e 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -44,8 +44,8 @@ void error_set_errno(Error **errp, int os_error, ErrorClass err_class,
  * printf-style human message, followed by a g_win32_error_message() string if
  * @win32_err is not zero.
  */
-void error_set_win32(Error **errp, int win32_err, ErrorClass err_class,
-                     const char *fmt, ...) GCC_FMT_ATTR(4, 5);
+void error_setg_win32(Error **errp, int win32_err, const char *fmt, ...)
+    GCC_FMT_ATTR(3, 4);
 #endif
 
 /**
@@ -56,11 +56,6 @@ void error_setg(Error **errp, const char *fmt, ...)
 #define error_setg_errno(errp, os_error, fmt, ...) \
     error_set_errno(errp, os_error, ERROR_CLASS_GENERIC_ERROR, \
                     fmt, ## __VA_ARGS__)
-#ifdef _WIN32
-#define error_setg_win32(errp, win32_err, fmt, ...) \
-    error_set_win32(errp, win32_err, ERROR_CLASS_GENERIC_ERROR, \
-                    fmt, ## __VA_ARGS__)
-#endif
 
 /**
  * Helper for open() errors
diff --git a/qga/vss-win32.c b/qga/vss-win32.c
index 0e4095736e..e1f539835c 100644
--- a/qga/vss-win32.c
+++ b/qga/vss-win32.c
@@ -150,9 +150,8 @@ void qga_vss_fsfreeze(int *nr_volume, Error **errp, bool freeze)
     const char *func_name = freeze ? "requester_freeze" : "requester_thaw";
     QGAVSSRequesterFunc func;
     ErrorSet errset = {
-        .error_set = (ErrorSetFunc)error_set_win32,
-        .errp = (void **)errp,
-        .err_class = ERROR_CLASS_GENERIC_ERROR
+        .error_setg_win32 = error_setg_win32,
+        .errp = errp,
     };
 
     func = (QGAVSSRequesterFunc)GetProcAddress(provider_lib, func_name);
diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp
index 922e74ddfc..b130fee934 100644
--- a/qga/vss-win32/requester.cpp
+++ b/qga/vss-win32/requester.cpp
@@ -24,7 +24,7 @@
 #define VSS_TIMEOUT_EVENT_MSEC 10
 
 #define err_set(e, err, fmt, ...) \
-    ((e)->error_set((e)->errp, err, (e)->err_class, fmt, ## __VA_ARGS__))
+    ((e)->error_setg_win32((e)->errp, err, fmt, ## __VA_ARGS__))
 #define err_is_set(e) ((e)->errp && *(e)->errp)
 
 
diff --git a/qga/vss-win32/requester.h b/qga/vss-win32/requester.h
index 374f9b8d16..0a8d048874 100644
--- a/qga/vss-win32/requester.h
+++ b/qga/vss-win32/requester.h
@@ -20,13 +20,14 @@
 extern "C" {
 #endif
 
+struct Error;
+
 /* Callback to set Error; used to avoid linking glib to the DLL */
-typedef void (*ErrorSetFunc)(void **errp, int win32_err, int err_class,
-                             const char *fmt, ...) GCC_FMT_ATTR(4, 5);
+typedef void (*ErrorSetFunc)(struct Error **errp, int win32_err,
+                             const char *fmt, ...) GCC_FMT_ATTR(3, 4);
 typedef struct ErrorSet {
-    ErrorSetFunc error_set;
-    void **errp;
-    int err_class;
+    ErrorSetFunc error_setg_win32;
+    struct Error **errp;
 } ErrorSet;
 
 STDAPI requester_init(void);
diff --git a/util/error.c b/util/error.c
index 8f12f67012..9620f2a1f6 100644
--- a/util/error.c
+++ b/util/error.c
@@ -96,8 +96,7 @@ void error_setg_file_open(Error **errp, int os_errno, const char *filename)
 
 #ifdef _WIN32
 
-void error_set_win32(Error **errp, int win32_err, ErrorClass err_class,
-                     const char *fmt, ...)
+void error_setg_win32(Error **errp, int win32_err, const char *fmt, ...)
 {
     va_list ap;
     char *msg1, *msg2;
@@ -107,7 +106,7 @@ void error_set_win32(Error **errp, int win32_err, ErrorClass err_class,
     }
 
     va_start(ap, fmt);
-    error_setv(errp, err_class, fmt, ap);
+    error_setv(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
     va_end(ap);
 
     if (win32_err != 0) {