diff --git a/src/packer.cpp b/src/packer.cpp
index 5548c708..2d96a0b9 100644
--- a/src/packer.cpp
+++ b/src/packer.cpp
@@ -1025,7 +1025,7 @@ void Packer::initLoader(const void *pdata, int plen, int pinfo, int small)
 }
 
 
-void Packer::addLoader(const char *s, ...)
+void __acc_cdecl_va Packer::addLoader(const char *s, ...)
 {
     const char *p;
     va_list ap;
diff --git a/src/packer.h b/src/packer.h
index 1ad89228..7a180264 100644
--- a/src/packer.h
+++ b/src/packer.h
@@ -208,7 +208,7 @@ protected:
     virtual const upx_byte *getLoader() const;
     virtual int getLoaderSize() const;
     virtual void initLoader(const void *pdata, int plen, int pinfo=-1, int small=-1);
-    virtual void addLoader(const char *s, ...);
+    virtual void __acc_cdecl_va addLoader(const char *s, ...);
     virtual int getLoaderSection(const char *name, int *slen=NULL) const;
     virtual int getLoaderSectionStart(const char *name, int *slen=NULL) const;
     virtual const char *getDecompressor() const;