diff --git a/src/hence/emulator.cr b/src/hence/emulator.cr
index f9470bb..269d1fd 100644
--- a/src/hence/emulator.cr
+++ b/src/hence/emulator.cr
@@ -79,7 +79,7 @@ module Hence
         @reg_inp = 0_u16,
         @reg_out = 0_u16,
         @stack = Slice(UInt16).new({{ 8 * 1024 }}),
-        @memory = Slice(UInt16).new({{ 24 * 1024 }})
+        @memory = Slice(UInt16).new({{ 16 * 1024 }})
       )
       end
 
@@ -226,8 +226,10 @@ module Hence
           @program[address].to_u16
         elsif address < {{ 40 * 1024 }}
           @stack[address - {{ 32 * 1024 }}]
-        else
+        elsif address < {{ 56 * 1024 }}
           @memory[address - {{ 40 * 1024 }}]
+        else
+          0_u16
         end
       end
 
@@ -238,8 +240,10 @@ module Hence
           @stack[address - {{ 32 * 1024 }}] = value
 
           value
-        else
+        elsif address < {{ 56 * 1024 }}
           @memory[address - {{ 40 * 1024 }}] = value
+        else
+          0_u16
         end
       end
     end
diff --git a/src/hence/firmware/documentation.md.ecr b/src/hence/firmware/documentation.md.ecr
index 693d6a4..048d5b7 100644
--- a/src/hence/firmware/documentation.md.ecr
+++ b/src/hence/firmware/documentation.md.ecr
@@ -29,7 +29,7 @@ Opcode | Name
 <% output = " " + output unless output.blank? -%>
 Opcode | Argument | Stack
 ---|---|---
-`0x<%= sorted_opcodes.find! { |opc| opc[1].name == opcode.name }[0].to_s(16).rjust(2, '0') %>` | <%= opcode.arg && "`#{opcode.arg}`" %> | <%= (opcode.stack.input.size > 0 && opcode.stack.output.size > 0) ? "`#{input}--#{output}`" : nil %>
+`0x<%= sorted_opcodes.find! { |opc| opc[1].name == opcode.name }[0].to_s(16).rjust(2, '0') %>` | <%= opcode.arg && "`#{opcode.arg}`" %> | <%= (opcode.stack.input.size > 0 || opcode.stack.output.size > 0) ? "`#{input}--#{output}`" : nil %>
 <%- if opcode.example -%>
 
 ```gnuassembler