diff --git a/target/hppa/insns.decode b/target/hppa/insns.decode
index 13c6a55bf2..f700fe472e 100644
--- a/target/hppa/insns.decode
+++ b/target/hppa/insns.decode
@@ -164,6 +164,8 @@ ixtlbx          000001 b:5 r:5 ... 000000 addr:1 0 00000        \
 
 # pcxl and pcxl2 Fast TLB Insert instructions
 ixtlbxf         000001 00000 r:5 00 0 data:1 01000 addr:1 0 00000
+# workaround for non-standard encoding as used in HP-UX 9
+ixtlbxf         000001 01001 r:5 01 0 data:1 01000 addr:1 0 00000
 
 # pa2.0 tlb insert idtlbt and iitlbt instructions
 ixtlbt          000001 r2:5 r1:5 000 data:1 100000 0 00000    # idtlbt