diff --git a/instrs.txt b/instrs.txt
index 8d6553b..ce90a43 100644
--- a/instrs.txt
+++ b/instrs.txt
@@ -1391,7 +1391,7 @@ df//5                 M     MEM64  -      -      -      FILD
 df//6                 M     FPU    -      -      -      FBSTP
 df//7                 M     MEM64  -      -      -      FISTP
 # FSTSW AX
-df//e0                O     GP16   -      -      -      FSTSW
+df//e0                A     GP16   -      -      -      FSTSW
 df//f0+               AO    FPU    FPU    -      -      FCOMIP
 df//f8+               AO    FPU    FPU    -      -      FUCOMIP
 #
diff --git a/parseinstrs.py b/parseinstrs.py
index 1b154ba..9de654a 100644
--- a/parseinstrs.py
+++ b/parseinstrs.py
@@ -69,6 +69,7 @@ ENCODINGS = {
     "OI": InstrFlags(modreg_idx=0^3, imm_idx=1^3, imm_control=4),
     "OA": InstrFlags(modreg_idx=0^3, zeroreg_idx=1^3),
     "AO": InstrFlags(modreg_idx=1^3, zeroreg_idx=0^3),
+    "A": InstrFlags(zeroreg_idx=0^3),
     "D": InstrFlags(imm_idx=0^3, imm_control=6),
     "FD": InstrFlags(zeroreg_idx=0^3, imm_idx=1^3, imm_control=2),
     "TD": InstrFlags(zeroreg_idx=1^3, imm_idx=0^3, imm_control=2),
diff --git a/tests/prefixes.txt b/tests/prefixes.txt
index a5d1f21..a14d865 100644
--- a/tests/prefixes.txt
+++ b/tests/prefixes.txt
@@ -29,3 +29,4 @@ decode   8ec0                           [MOV_G2S reg0:r0 reg4:r0]
 decode   8ec8                           UD
 decode   d8c1                           [FADD reg0:r0 reg0:r1]
 decode64 41d8c1                         [FADD reg0:r0 reg0:r1]
+decode64 41dfe0                         [FSTSW reg2:r0]