diff --git a/src/p_vmlinx.cpp b/src/p_vmlinx.cpp
index 0a3ca42e..5c4b4c20 100644
--- a/src/p_vmlinx.cpp
+++ b/src/p_vmlinx.cpp
@@ -271,7 +271,8 @@ void PackVmlinuxBase<T>::pack(OutputFile *fo)
     defineDecompressorSymbols();
     defineFilterSymbols(linker, &ft);
     if (0x40==(0xf0 & ft.id)) {
-        linker->defineSymbol("filter_length", ph.u_len); // redefine
+        linker->defineSymbol("filter_length", ft.buf_len); // redefine
+        assert(ft.buf_len == ph.u_len);
     }
     relocateLoader();
 
diff --git a/src/p_vmlinz.cpp b/src/p_vmlinz.cpp
index 4a1e1cf5..57a0a95d 100644
--- a/src/p_vmlinz.cpp
+++ b/src/p_vmlinz.cpp
@@ -445,7 +445,8 @@ void PackBvmlinuzI386::pack(OutputFile *fo)
 
     defineFilterSymbols(linker, &ft);
     if (0x40==(0xf0 & ft.id)) {
-        linker->defineSymbol("filter_length", ph.u_len); // redefine
+        linker->defineSymbol("filter_length", ft.buf_len); // redefine
+        assert(ft.buf_len == ph.u_len);
     }
     defineDecompressorSymbols();
     linker->defineSymbol("original_entry", physical_start);