diff --git a/lib/Target/ARM/ARMInstrThumb2.td b/lib/Target/ARM/ARMInstrThumb2.td
index 8ba2376..c950fcb 100644
--- a/lib/Target/ARM/ARMInstrThumb2.td
+++ b/lib/Target/ARM/ARMInstrThumb2.td
@@ -1352,8 +1352,12 @@
 defm t2UXTB16 : T2I_unary_rrot_uxtb16<0b011, "uxtb16",
                                UnOpFrag<(and node:$Src, 0x00FF00FF)>>;
 
-def : T2Pat<(and (shl GPR:$Src, (i32 8)), 0xFF00FF),
-            (t2UXTB16r_rot GPR:$Src, 24)>, Requires<[HasT2ExtractPack]>;
+// FIXME: This pattern incorrectly assumes the shl operator is a rotate.
+//        The transformation should probably be done as a combiner action
+//        instead so we can include a check for masking back in the upper
+//        eight bits of the source into the lower eight bits of the result.
+//def : T2Pat<(and (shl GPR:$Src, (i32 8)), 0xFF00FF),
+//            (t2UXTB16r_rot GPR:$Src, 24)>, Requires<[HasT2ExtractPack]>;
 def : T2Pat<(and (srl GPR:$Src, (i32 8)), 0xFF00FF),
             (t2UXTB16r_rot GPR:$Src, 8)>, Requires<[HasT2ExtractPack]>;