diff --git a/src/arm/decoder-thumb.c b/src/arm/decoder-thumb.c
index 3cdf6a1c7..d0fdcedf5 100644
--- a/src/arm/decoder-thumb.c
+++ b/src/arm/decoder-thumb.c
@@ -126,7 +126,7 @@ DEFINE_DATA_FORM_5_DECODER_THUMB(ASR2, ASR, ARM_OPERAND_AFFECTED_1)
 DEFINE_DATA_FORM_5_DECODER_THUMB(ADC, ADC, ARM_OPERAND_AFFECTED_1)
 DEFINE_DATA_FORM_5_DECODER_THUMB(SBC, SBC, ARM_OPERAND_AFFECTED_1)
 DEFINE_DATA_FORM_5_DECODER_THUMB(ROR, ROR, ARM_OPERAND_AFFECTED_1)
-DEFINE_DATA_FORM_5_DECODER_THUMB(TST, TST, ARM_OPERAND_AFFECTED_1)
+DEFINE_DATA_FORM_5_DECODER_THUMB(TST, TST, ARM_OPERAND_NONE)
 DEFINE_DATA_FORM_5_DECODER_THUMB(NEG, NEG, ARM_OPERAND_AFFECTED_1)
 DEFINE_DATA_FORM_5_DECODER_THUMB(CMP2, CMP, ARM_OPERAND_NONE)
 DEFINE_DATA_FORM_5_DECODER_THUMB(CMN, CMN, ARM_OPERAND_NONE)