diff --git a/Asm65/OpDef.cs b/Asm65/OpDef.cs
index 0eeb77f..9447324 100644
--- a/Asm65/OpDef.cs
+++ b/Asm65/OpDef.cs
@@ -709,6 +709,12 @@ namespace Asm65 {
             }
             return flags;
         }
+        private static StatusFlags FlagUpdater_LSR(StatusFlags flags, int immVal,
+                ref StatusFlags condBranchTakenFlags) {
+            flags.C = flags.Z = TriState16.INDETERMINATE;
+            flags.N = 0;    // always shifts 0 into high bit
+            return flags;
+        }
         private static StatusFlags FlagUpdater_ROL(StatusFlags flags, int immVal,
                 ref StatusFlags condBranchTakenFlags) {
             // this rotates the N flag into C, so set C=N
@@ -1152,7 +1158,7 @@ namespace Asm65 {
             Effect = FlowEffect.Cont,
             BaseMemEffect = MemoryEffect.ReadModifyWrite,
             FlagsAffected = FlagsAffected_NZC,
-            StatusFlagUpdater = FlagUpdater_NZC
+            StatusFlagUpdater = FlagUpdater_LSR
         };
         private static OpDef OpMVN = new OpDef() {
             Mnemonic = OpName.MVN,
diff --git a/SourceGen/SGTestData/1003-flags-and-branches b/SourceGen/SGTestData/1003-flags-and-branches
index 34e3a42..0f2797d 100644
Binary files a/SourceGen/SGTestData/1003-flags-and-branches and b/SourceGen/SGTestData/1003-flags-and-branches differ
diff --git a/SourceGen/SGTestData/Expected/1003-flags-and-branches_64tass.S b/SourceGen/SGTestData/Expected/1003-flags-and-branches_64tass.S
index c17aff3..e87ab2f 100644
--- a/SourceGen/SGTestData/Expected/1003-flags-and-branches_64tass.S
+++ b/SourceGen/SGTestData/Expected/1003-flags-and-branches_64tass.S
@@ -219,50 +219,57 @@ _L10F2  lda     #$00
         .byte   $00
         .byte   $dc
 
-_L10FA  clc
+_L10FA  lda     #$ff
+        lsr     a
+        bpl     _L1101
+
+        .byte   $00
+        .byte   $dd
+
+_L1101  clc
         php
         sec
         plp
-        bcc     _L1102
+        bcc     _L1109
 
         .byte   $00
         .byte   $00
 
-_L1102  sec
-        bcs     _L1106
+_L1109  sec
+        bcs     _L110D
 
-_L1105  clc
-_L1106  lda     $33
-        beq     _L1105
-        bcs     _L110E
+_L110C  clc
+_L110D  lda     $33
+        beq     _L110C
+        bcs     _L1115
         lda     $44
-_L110E  nop
+_L1115  nop
         rep     #$20
         .al
         sep     #$10
-        jsr     _L112A
+        jsr     _L1131
         rep     #$30
         .xl
-        jsr     _L1130
+        jsr     _L1137
         sep     #$30
         .as
         .xs
-        jsr     _L1130
+        jsr     _L1137
         rep     #$20
         .al
         sep     #$10
-        jsr     _L112A
+        jsr     _L1131
         sep     #$30
         .as
         rts
 
         .al
-_L112A  lda     #$1234
+_L1131  lda     #$1234
         ldx     #$ff
         rts
 
         .as
-_L1130  lda     #$ff
+_L1137  lda     #$ff
         ldx     #$ee
         ldy     #$dd
         rts
diff --git a/SourceGen/SGTestData/Expected/1003-flags-and-branches_Merlin32.S b/SourceGen/SGTestData/Expected/1003-flags-and-branches_Merlin32.S
index 4b40d90..d8ea883 100644
--- a/SourceGen/SGTestData/Expected/1003-flags-and-branches_Merlin32.S
+++ b/SourceGen/SGTestData/Expected/1003-flags-and-branches_Merlin32.S
@@ -214,49 +214,56 @@ L105F    sep   #$80
          dfb   $00
          dfb   $dc
 
-:L10FA   clc
+:L10FA   lda   #$ff
+         lsr   A
+         bpl   :L1101
+
+         dfb   $00
+         dfb   $dd
+
+:L1101   clc
          php
          sec
          plp
-         bcc   :L1102
+         bcc   :L1109
 
          dfb   $00
          dfb   $00
 
-:L1102   sec
-         bcs   :L1106
+:L1109   sec
+         bcs   :L110D
 
-:L1105   clc
-:L1106   lda   $33
-         beq   :L1105
-         bcs   :L110E
+:L110C   clc
+:L110D   lda   $33
+         beq   :L110C
+         bcs   :L1115
          lda   $44
-:L110E   nop
+:L1115   nop
          rep   #$20
          mx    %01
          sep   #$10
-         jsr   :L112A
+         jsr   :L1131
          rep   #$30
          mx    %00
-         jsr   :L1130
+         jsr   :L1137
          sep   #$30
          mx    %11
-         jsr   :L1130
+         jsr   :L1137
          rep   #$20
          mx    %01
          sep   #$10
-         jsr   :L112A
+         jsr   :L1131
          sep   #$30
          mx    %11
          rts
 
          mx    %01
-:L112A   lda   #$1234
+:L1131   lda   #$1234
          ldx   #$ff
          rts
 
          mx    %11
-:L1130   lda   #$ff
+:L1137   lda   #$ff
          ldx   #$ee
          ldy   #$dd
          rts
diff --git a/SourceGen/SGTestData/Expected/1003-flags-and-branches_acme.S b/SourceGen/SGTestData/Expected/1003-flags-and-branches_acme.S
index 24ef94d..545263c 100644
--- a/SourceGen/SGTestData/Expected/1003-flags-and-branches_acme.S
+++ b/SourceGen/SGTestData/Expected/1003-flags-and-branches_acme.S
@@ -219,50 +219,57 @@ L105F   sep     #$80
         !byte   $00
         !byte   $dc
 
-@L10FA  clc
+@L10FA  lda     #$ff
+        lsr
+        bpl     @L1101
+
+        !byte   $00
+        !byte   $dd
+
+@L1101  clc
         php
         sec
         plp
-        bcc     @L1102
+        bcc     @L1109
 
         !byte   $00
         !byte   $00
 
-@L1102  sec
-        bcs     @L1106
+@L1109  sec
+        bcs     @L110D
 
-@L1105  clc
-@L1106  lda     $33
-        beq     @L1105
-        bcs     @L110E
+@L110C  clc
+@L110D  lda     $33
+        beq     @L110C
+        bcs     @L1115
         lda     $44
-@L110E  nop
+@L1115  nop
         rep     #$20
         !al
         sep     #$10
-        jsr     @L112A
+        jsr     @L1131
         rep     #$30
         !rl
-        jsr     @L1130
+        jsr     @L1137
         sep     #$30
         !as
         !rs
-        jsr     @L1130
+        jsr     @L1137
         rep     #$20
         !al
         sep     #$10
-        jsr     @L112A
+        jsr     @L1131
         sep     #$30
         !as
         rts
 
         !al
-@L112A  lda     #$1234
+@L1131  lda     #$1234
         ldx     #$ff
         rts
 
         !as
-@L1130  lda     #$ff
+@L1137  lda     #$ff
         ldx     #$ee
         ldy     #$dd
         rts
diff --git a/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.S b/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.S
index 95971b2..f65691e 100644
--- a/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.S
+++ b/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.S
@@ -220,50 +220,57 @@ L105F:   sep     #$80
          .byte   $00
          .byte   $dc
 
-@L10FA:  clc
+@L10FA:  lda     #$ff
+         lsr     A
+         bpl     @L1101
+
+         .byte   $00
+         .byte   $dd
+
+@L1101:  clc
          php
          sec
          plp
-         bcc     @L1102
+         bcc     @L1109
 
          .byte   $00
          .byte   $00
 
-@L1102:  sec
-         bcs     @L1106
+@L1109:  sec
+         bcs     @L110D
 
-@L1105:  clc
-@L1106:  lda     $33
-         beq     @L1105
-         bcs     @L110E
+@L110C:  clc
+@L110D:  lda     $33
+         beq     @L110C
+         bcs     @L1115
          lda     $44
-@L110E:  nop
+@L1115:  nop
          rep     #$20
          .a16
          sep     #$10
-         jsr     @L112A
+         jsr     @L1131
          rep     #$30
          .i16
-         jsr     @L1130
+         jsr     @L1137
          sep     #$30
          .a8
          .i8
-         jsr     @L1130
+         jsr     @L1137
          rep     #$20
          .a16
          sep     #$10
-         jsr     @L112A
+         jsr     @L1131
          sep     #$30
          .a8
          rts
 
          .a16
-@L112A:  lda     #$1234
+@L1131:  lda     #$1234
          ldx     #$ff
          rts
 
          .a8
-@L1130:  lda     #$ff
+@L1137:  lda     #$ff
          ldx     #$ee
          ldy     #$dd
          rts
diff --git a/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.cfg b/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.cfg
index 1fd5402..c1cdbb0 100644
--- a/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.cfg
+++ b/SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.cfg
@@ -1,7 +1,7 @@
 # 6502bench SourceGen generated linker script for 1003-flags-and-branches
 MEMORY {
     MAIN: file=%O, start=%S, size=65536;
-#    MEM000: file=%O, start=$1000, size=311;
+#    MEM000: file=%O, start=$1000, size=318;
 }
 SEGMENTS {
     CODE: load=MAIN, type=rw;
diff --git a/SourceGen/SGTestData/Source/1003-flags-and-branches.S b/SourceGen/SGTestData/Source/1003-flags-and-branches.S
index 059510f..26ba38d 100644
--- a/SourceGen/SGTestData/Source/1003-flags-and-branches.S
+++ b/SourceGen/SGTestData/Source/1003-flags-and-branches.S
@@ -195,6 +195,13 @@ ok_ror2
         brk     $dc
 ok_rol1
 
+; check lsr
+        lda     #$ff
+        lsr     A           ;lsr always clears the high bit
+        bpl     ok_lsr
+        brk     $dd
+ok_lsr
+
 ; simple php/plp pair test
         clc
         php