diff --git a/win32/clamav-for-windows/sigui/SigUI/installdb.cpp b/win32/clamav-for-windows/sigui/SigUI/installdb.cpp
index a9a308918..04d723e97 100644
--- a/win32/clamav-for-windows/sigui/SigUI/installdb.cpp
+++ b/win32/clamav-for-windows/sigui/SigUI/installdb.cpp
@@ -256,7 +256,7 @@ bool SigUICopy::copySignatures(const wxString &staging)
     return OK;
 }
 
-int SigUICopy::sigprogress(const char* WXUNUSED(type), const char* WXUNUSED(name), void *context)
+int SigUICopy::sigprogress(const char* WXUNUSED(type), const char* WXUNUSED(name), unsigned int WXUNUSED(custom), void *context)
 {
     SigUICopy *p = (SigUICopy*)context;
     if (++p->cnt % 1000)
diff --git a/win32/clamav-for-windows/sigui/SigUI/installdb.h b/win32/clamav-for-windows/sigui/SigUI/installdb.h
index b17f68389..9ad40e318 100644
--- a/win32/clamav-for-windows/sigui/SigUI/installdb.h
+++ b/win32/clamav-for-windows/sigui/SigUI/installdb.h
@@ -40,7 +40,7 @@ class SigUICopy
 		bool copySignatures(const wxString &staging);
 		bool loadDB(const wxString& dir);
 		bool canceled(void);
-		static int sigprogress(const char *type, const char *name, void *context);
+		static int sigprogress(const char *type, const char *name, unsigned int custom, void *context);
 };
 
 #endif