diff --git a/src/mon_m65/bsmon.s b/src/mon_m65/bsmon.s
index 0a3c7259..5f5be446 100644
--- a/src/mon_m65/bsmon.s
+++ b/src/mon_m65/bsmon.s
@@ -195,7 +195,7 @@ Jump_Table:
          !word Mon_Disassemble  ; D
          !word Mon_Fill         ; F
          !word Mon_Go           ; G  XXX to be debugged/adapted
-         !word Mon_Hunt         ; H  XXX to be bugfixed
+         !word Mon_Hunt         ; H
          !word Mon_JSR          ; J  XXX to be debugged/adapted
          !word Mon_Memory       ; M
          !word Mon_Register     ; R
diff --git a/src/mon_m65/mon_command_fill.s b/src/mon_m65/mon_command_fill.s
index 9a9de779..e79f5ca0 100644
--- a/src/mon_m65/mon_command_fill.s
+++ b/src/mon_m65/mon_command_fill.s
@@ -11,10 +11,7 @@ Mon_Fill:
 
 	jsr  Get_Addr_To_LAC   ; Long_AC = fill byte
 	+beq Mon_Error
-	lda  Long_AC+1
-	ora  Long_AC+2
-	ora  Long_AC+3
-	+bne Mon_Error         ; only 1 fill byte allowed
+	jsr  Syntax_Byte_AC    ; only 1 fill byte allowed
 
 	ldz  #$00
 
diff --git a/src/mon_m65/mon_command_hunt.s b/src/mon_m65/mon_command_hunt.s
index b8cd50f1..048851a5 100644
--- a/src/mon_m65/mon_command_hunt.s
+++ b/src/mon_m65/mon_command_hunt.s
@@ -28,6 +28,7 @@ Mon_Hunt:
 @bin:
 
 	jsr  Got_Addr_To_LAC
+	jsr  Syntax_Byte_AC
 
 @lpbin:
 
@@ -36,10 +37,7 @@ Mon_Hunt:
 	iny
 	jsr  Get_Addr_To_LAC
 	beq  @hunt
-	lda  Long_AC+1
-	ora  Long_AC+2
-	ora  Long_AC+3
-	+bne Mon_Error         ; value above $FF	
+	jsr  Syntax_Byte_AC
 
 	cpy  #32               ; max data length
 	bne  @lpbin
diff --git a/src/mon_m65/mon_helper_get_addr_to_lac.s b/src/mon_m65/mon_helper_get_addr_to_lac.s
index d57c3e55..7bfb8d2b 100644
--- a/src/mon_m65/mon_helper_get_addr_to_lac.s
+++ b/src/mon_m65/mon_helper_get_addr_to_lac.s
@@ -40,7 +40,7 @@ Get_Addr_To_LAC:
    ; at this point .Y value determines a numeric system
 
    jsr  Get_Char
-   beq  @exit                ; '?', ':'', ';' and zero terminate
+   beq  @exit                ; branch if terminated
    cmp  #'0'
    bcc  @exit
    cmp  #':'
diff --git a/src/mon_m65/mon_helper_syntax.s b/src/mon_m65/mon_helper_syntax.s
new file mode 100644
index 00000000..ff77a4d5
--- /dev/null
+++ b/src/mon_m65/mon_helper_syntax.s
@@ -0,0 +1,17 @@
+
+; Monitor helper code - syntax checking
+
+
+Syntax_Byte_AC:            ; ensure AC contains a 1-byte value
+
+	php
+	pha
+
+	lda  Long_AC+1
+	ora  Long_AC+2
+	ora  Long_AC+3
+	+bne Mon_Error         ; value above $FF
+
+	pla
+	plp
+	rts