diff --git a/lips/Dumper.lua b/lips/Dumper.lua
index a568fa0..769d989 100644
--- a/lips/Dumper.lua
+++ b/lips/Dumper.lua
@@ -13,13 +13,6 @@ local Reader = require(path.."Reader")
 
 local bitrange = util.bitrange
 
-local function label_delta(from, to)
-    -- TODO: consider removing the % here since .base should handle that now
-    to = to
-    from = from
-    return floor(to/4) - 1 - floor(from/4)
-end
-
 local Dumper = Reader:extend()
 function Dumper:init(writer, options)
     self.writer = writer
@@ -42,13 +35,17 @@ function Dumper:export_labels(t)
     return t
 end
 
+function Dumper:label_delta(from, to)
+    local rel = floor(to/4) - 1 - floor(from/4)
+    if rel > 0x8000 or rel <= -0x8000 then
+        self:error('branch too far', rel)
+    end
+    return rel % 0x10000
+end
+
 function Dumper:desym(t)
     if t.tt == 'REL' then
-        local rel = label_delta(self:pc(), t.tok)
-        if rel > 0x8000 or rel <= -0x8000 then
-            self:error('branch too far')
-        end
-        return rel % 0x10000
+        return self:label_delta(self:pc(), t.tok)
     elseif type(t.tok) == 'number' then
         if t.offset then
             return t.tok + t.offset
@@ -69,11 +66,7 @@ function Dumper:desym(t)
             return label
         end
 
-        local rel = label_delta(self:pc(), label)
-        if rel > 0x8000 or rel <= -0x8000 then
-            self:error('branch too far')
-        end
-        return rel % 0x10000
+        return self:label_delta(self:pc(), label)
     end
     error('Internal Error: failed to desym')
 end
@@ -81,7 +74,7 @@ end
 function Dumper:validate(n, bits)
     local max = 2^bits
     if n == nil then
-        self:error('value is nil') -- internal error?
+        error('Internal Error: number to validate is nil', 2)
     end
     if n > max or n < 0 then
         self:error('value out of range', ("%X"):format(n))
@@ -110,34 +103,6 @@ function Dumper:write(t)
     end
 end
 
-function Dumper:dump_instruction(t)
-    local uw = 0
-    local lw = 0
-
-    local o = t[1]
-    uw = uw + o*0x400
-
-    if #t == 2 then
-        local val = self:valvar(t[2], 26)
-        uw = uw + bitrange(val, 16, 25)
-        lw = lw + bitrange(val, 0, 15)
-    elseif #t == 4 then
-        uw = uw + self:valvar(t[2], 5)*0x20
-        uw = uw + self:valvar(t[3], 5)
-        lw = lw + self:valvar(t[4], 16)
-    elseif #t == 6 then
-        uw = uw + self:valvar(t[2], 5)*0x20
-        uw = uw + self:valvar(t[3], 5)
-        lw = lw + self:valvar(t[4], 5)*0x800
-        lw = lw + self:valvar(t[5], 5)*0x40
-        lw = lw + self:valvar(t[6], 6)
-    else
-        error('Internal Error: unknown n-size')
-    end
-
-    return uw, lw
-end
-
 function Dumper:assemble_j(first, out)
     local w = 0
     w = w + self:valvar(first,   6) * 0x04000000
@@ -349,7 +314,7 @@ function Dumper:load(statements)
                     local align = s[1] and s[1].tok or 2
                     content = s[2] and s[2].tok or 0
                     if align < 0 then
-                        self:error('negative alignment')
+                        self:error('negative alignment', align)
                     else
                         align = 2^align
                     end
diff --git a/lips/Lexer.lua b/lips/Lexer.lua
index 3bde74e..aa86c39 100644
--- a/lips/Lexer.lua
+++ b/lips/Lexer.lua
@@ -249,7 +249,7 @@ function Lexer:lex_string(yield)
     local bytes = {}
     while true do
         if self.chr == '\n' then
-            self:error('unimplemented')
+            self:error('unimplemented: newlines in strings')
             yield('EOL', '\n')
             self:nextc()
         elseif self.ord == self.EOF then
diff --git a/lips/Muncher.lua b/lips/Muncher.lua
index b3f52fa..355ee6c 100644
--- a/lips/Muncher.lua
+++ b/lips/Muncher.lua
@@ -56,7 +56,7 @@ function Muncher:expect_EOL()
         self:advance()
         return
     end
-    self:error('expected end of line')
+    self:error('expected end of line', self.tt)
 end
 
 function Muncher:optional_comma()
@@ -68,7 +68,7 @@ end
 
 function Muncher:number()
     if self.tt ~= 'NUM' then
-        self:error('expected number')
+        self:error('expected number', self.tt)
     end
     local t = self.t
     self:advance()
@@ -77,7 +77,7 @@ end
 
 function Muncher:string()
     if self.tt ~= 'STRING' then
-        self:error('expected string')
+        self:error('expected string', self.tt)
     end
     local t = self.t
     self:advance()
@@ -87,11 +87,11 @@ end
 function Muncher:register(registers)
     registers = registers or data.registers
     if self.tt ~= 'REG' then
-        self:error('expected register')
+        self:error('expected register', self.tt)
     end
     local t = self.t
     if not registers[t.tok] then
-        self:error('wrong type of register')
+        self:error('wrong type of register', t.tok)
     end
     self:advance()
     return self:token(t)
@@ -99,16 +99,16 @@ end
 
 function Muncher:deref()
     if self.tt ~= 'OPEN' then
-        self:error('expected opening parenthesis for dereferencing')
+        self:error('expected opening parenthesis for dereferencing', self.tt)
     end
     self:advance()
     if self.tt ~= 'REG' then
-        self:error('expected register to dereference')
+        self:error('expected register to dereference', self.tt)
     end
     local t = self.t
     self:advance()
     if self.tt ~= 'CLOSE' then
-        self:error('expected closing parenthesis for dereferencing')
+        self:error('expected closing parenthesis for dereferencing', self.tt)
     end
     self:advance()
     return self:token(t)
@@ -119,7 +119,7 @@ function Muncher:const(relative, no_label)
         self:error('expected constant', self.tt)
     end
     if no_label and self.tt == 'LABELSYM' then
-        self:error('labels are not allowed here')
+        self:error('labels are not allowed here', self.tt)
     end
     local t = self:token(self.t)
     if relative then
@@ -135,19 +135,19 @@ end
 
 function Muncher:special()
     if self.tt ~= 'SPECIAL' then
-        self:error('expected special name to call')
+        self:error('expected special name to call', self.tt)
     end
     local name = self.tok
     self:advance()
     if self.tt ~= 'OPEN' then
-        self:error('expected opening parenthesis for special call')
+        self:error('expected opening parenthesis for special call', self.tt)
     end
 
     local args = {}
     while true do
         local arg = self:advance()
         if not arg_types[arg.tt] then
-            self:error('invalid argument type')
+            self:error('invalid argument type', arg.tt)
         else
             self:advance()
         end
@@ -157,7 +157,7 @@ function Muncher:special()
             insert(args, arg)
             break
         else
-            self:error('unexpected token in argument list')
+            self:error('unexpected token in argument list', self.tt)
         end
     end
 
diff --git a/lips/Preproc.lua b/lips/Preproc.lua
index 7a09e22..60ba783 100644
--- a/lips/Preproc.lua
+++ b/lips/Preproc.lua
@@ -90,7 +90,8 @@ function Preproc:check(s, i, tt)
     i = i or self.i
     local t = s[i]
     if t == nil then
-        self:error("expected another argument")
+        local err = ("expected another argument for %s at position %i"):format(self.s.type, self.i)
+        self:error(err)
     end
 
     self.fn = t.fn
diff --git a/lips/Reader.lua b/lips/Reader.lua
index 8c31484..f405edb 100644
--- a/lips/Reader.lua
+++ b/lips/Reader.lua
@@ -27,7 +27,8 @@ end
 function Reader:expect(tts)
     local t = self.s[self.i]
     if t == nil then
-        self:error("expected another argument") -- TODO: more verbose
+        local err = ("expected another argument for %s at position %i"):format(self.s.type, self.i)
+        self:error(err)
     end
 
     self.fn = t.fn
@@ -39,8 +40,12 @@ function Reader:expect(tts)
         end
     end
 
-    --local err = ("argument %i of %s expected type %s"):format(self.i, self.s.type, tt)
-    local err = ("unexpected type for argument %i of %s"):format(self.i, self.s.type)
+    local err
+    if #tts == 1 then
+        err = ("argument %i of %s expected type %s"):format(self.i, self.s.type, tts[1])
+    else
+        err = ("unexpected type for argument %i of %s"):format(self.i, self.s.type)
+    end
     self:error(err, t.tt)
 end
 
@@ -49,7 +54,7 @@ function Reader:register(registers)
     local t = self.s[self.i]
     local numeric = registers[t.tok]
     if not numeric then
-        self:error('wrong type of register')
+        self:error('wrong type of register', t.tok)
     end
     local new = Token(t)
     return new