diff --git a/src/p_lx_elf.cpp b/src/p_lx_elf.cpp
index 48f8797a..19be9d3d 100644
--- a/src/p_lx_elf.cpp
+++ b/src/p_lx_elf.cpp
@@ -401,10 +401,7 @@ void PackLinuxI386elf::pack(OutputFile *fo)
     ph.c_len = total_out;
 
     // write packheader
-    const int hsize = ph.getPackHeaderSize();
-    set_le32(obuf, UPX_MAGIC_LE32);             // note: always le32
-    patchPackHeader(obuf, hsize);
-    fo->write(obuf, hsize);
+    writePackHeader(fo);
 
     // write overlay offset (needed for decompression)
     set_native32(obuf, lsize);
diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index 207f03df..5e3c4d1c 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -75,6 +75,23 @@ bool PackUnix::canPack()
 }
 
 
+void PackUnix::writePackHeader(OutputFile *fo)
+{
+    unsigned char buf[32];
+    memset(buf, 0, sizeof(buf));
+
+    const int hsize = ph.getPackHeaderSize();
+    assert((unsigned)hsize <= sizeof(buf));
+
+    // note: magic constants are always le32
+    set_le32(buf+0, UPX_MAGIC_LE32);
+    set_le32(buf+4, UPX_MAGIC2_LE32);
+
+    patchPackHeader(buf, hsize);
+    fo->write(buf, hsize);
+}
+
+
 /*************************************************************************
 // Generic Unix pack(). Subclasses must provide patchLoader().
 //
@@ -186,10 +203,7 @@ void PackUnix::pack(OutputFile *fo)
     ph.c_len = total_out;
 
     // write packheader
-    const int hsize = ph.getPackHeaderSize();
-    set_le32(obuf, UPX_MAGIC_LE32);             // note: always le32
-    patchPackHeader(obuf, hsize);
-    fo->write(obuf, hsize);
+    writePackHeader(fo);
 
     // write overlay offset (needed for decompression)
     set_native32(obuf, lsize);
diff --git a/src/p_unix.h b/src/p_unix.h
index 5a9d987b..af3c6034 100644
--- a/src/p_unix.h
+++ b/src/p_unix.h
@@ -56,6 +56,8 @@ protected:
     virtual void patchLoaderChecksum() {}
     virtual void updateLoader(OutputFile *) = 0;
 
+    virtual void writePackHeader(OutputFile *fo);
+
     // in order too share as much code as possible we introduce
     // an endian abstraction here
     virtual unsigned get_native32(const void *, int off=0) = 0;