diff --git a/src/main/resources/assets/computercraft/lua/bios.lua b/src/main/resources/assets/computercraft/lua/bios.lua
index a06743eb2..7115538a5 100644
--- a/src/main/resources/assets/computercraft/lua/bios.lua
+++ b/src/main/resources/assets/computercraft/lua/bios.lua
@@ -6,6 +6,18 @@ if _VERSION == "Lua 5.1" then
     local nativeloadstring = loadstring
     local nativesetfenv = setfenv
     function load( x, name, mode, env )
+        if type( x ) ~= "string" then
+            error( "bad argument #1 (expected string, got " .. type( x ) .. ")", 2 ) 
+        end
+        if name ~= nil and type( name ) ~= "string" then
+            error( "bad argument #2 (expected string, got " .. type( name ) .. ")", 2 ) 
+        end
+        if mode ~= nil and type( mode ) ~= "string" then
+            error( "bad argument #3 (expected string, got " .. type( mode ) .. ")", 2 ) 
+        end
+        if env ~= nil and type( env) ~= "table" then
+            error( "bad argument #4 (expected table, got " .. type( env ) .. ")", 2 ) 
+        end
         if mode ~= nil and mode ~= "t" then
             error( "Binary chunk loading prohibited", 2 )
         end
@@ -709,6 +721,9 @@ if http then
         if _headers ~= nil and type( _headers ) ~= "table" then
             error( "bad argument #2 (expected table, got " .. type( _headers ) .. ")", 2 ) 
         end
+        if _binary ~= nil and type( _binary ) ~= "boolean" then
+            error( "bad argument #3 (expected boolean, got " .. type( _binary ) .. ")", 2 ) 
+        end
         return wrapRequest( _url, nil, _headers, _binary)
     end
 
@@ -722,6 +737,9 @@ if http then
         if _headers ~= nil and type( _headers ) ~= "table" then
             error( "bad argument #3 (expected table, got " .. type( _headers ) .. ")", 2 ) 
         end
+        if _binary ~= nil and type( _binary ) ~= "boolean" then
+            error( "bad argument #4 (expected boolean, got " .. type( _binary ) .. ")", 2 ) 
+        end
         return wrapRequest( _url, _post or "", _headers, _binary)
     end
 
@@ -735,6 +753,9 @@ if http then
         if _headers ~= nil and type( _headers ) ~= "table" then
             error( "bad argument #3 (expected table, got " .. type( _headers ) .. ")", 2 ) 
         end
+        if _binary ~= nil and type( _binary ) ~= "boolean" then
+            error( "bad argument #4 (expected boolean, got " .. type( _binary ) .. ")", 2 ) 
+        end
         local ok, err = nativeHTTPRequest( _url, _post, _headers, _binary )
         if not ok then
             os.queueEvent( "http_failure", _url, err )
diff --git a/src/main/resources/assets/computercraft/lua/rom/apis/io.lua b/src/main/resources/assets/computercraft/lua/rom/apis/io.lua
index d93ef9fdf..71e792164 100644
--- a/src/main/resources/assets/computercraft/lua/rom/apis/io.lua
+++ b/src/main/resources/assets/computercraft/lua/rom/apis/io.lua
@@ -49,11 +49,14 @@ function input( _arg )
 	elseif _G.type( _arg ) == "nil" then
 		return g_currentInput
 	else
-		error( "Expected file name or file handle" )
+		error( "bad argument #1 (expected string/table/nil, got " .. type( _arg ) .. ")", 2 )
 	end
 end
 
 function lines( _sFileName )
+    if type( _sFileNamel ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sFileName ) .. ")", 2 )
+    end
 	if _sFileName then
 		return open( _sFileName, "r" ):lines()
 	else
@@ -62,6 +65,12 @@ function lines( _sFileName )
 end
 
 function open( _sPath, _sMode )
+    if type( _sPath ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sPath ) .. ")", 2 )
+    end
+    if type( _sMode ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( _sMode ) .. ")", 2 )
+    end
 	local sMode = _sMode or "r"
 	local file, err = fs.open( _sPath, sMode )
 	if not file then
@@ -158,7 +167,7 @@ function output( _arg )
 	elseif _G.type( _arg ) == "nil" then
 		return g_currentOutput
 	else
-		error( "Expected file name or file handle" )
+		error( "bad argument #1 (expected string/table/nil, got " .. type( _arg ) .. ")", 2 )
 	end
 end
 
diff --git a/src/main/resources/assets/computercraft/lua/rom/apis/rednet.lua b/src/main/resources/assets/computercraft/lua/rom/apis/rednet.lua
index 1cc0c4ce2..9c5e2289e 100644
--- a/src/main/resources/assets/computercraft/lua/rom/apis/rednet.lua
+++ b/src/main/resources/assets/computercraft/lua/rom/apis/rednet.lua
@@ -8,7 +8,7 @@ local tHostnames = {}
 
 function open( sModem )
     if type( sModem ) ~= "string" then
-        error( "expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sModem ) .. ")", 2 )
     end
     if peripheral.getType( sModem ) ~= "modem" then 
         error( "No such modem: "..sModem, 2 )
@@ -21,7 +21,7 @@ function close( sModem )
     if sModem then
         -- Close a specific modem
         if type( sModem ) ~= "string" then
-            error( "expected string", 2 )
+            error( "bad argument #1 (expected string, got " .. type( sModem ) .. ")", 2 )
         end
         if peripheral.getType( sModem ) ~= "modem" then
             error( "No such modem: "..sModem, 2 )
@@ -42,7 +42,7 @@ function isOpen( sModem )
     if sModem then
         -- Check if a specific modem is open
         if type( sModem ) ~= "string" then
-            error( "expected string", 2 )
+            error( "bad argument #1 (expected string, got " .. type( sModem ) .. ")", 2 )
         end
         if peripheral.getType( sModem ) == "modem" then
             return peripheral.call( sModem, "isOpen", os.getComputerID() ) and peripheral.call( sModem, "isOpen", CHANNEL_BROADCAST )
@@ -59,6 +59,12 @@ function isOpen( sModem )
 end
 
 function send( nRecipient, message, sProtocol )
+    if type( nRecipient ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( nRecipient ) .. ")", 2 )
+    end
+    if sProtocol ~= nil and type( sProtocol ) ~= "string" then
+        error( "bad argument #3 (expected string, got " .. type( sProtocol ) .. ")", 2 )
+    end
     -- Generate a (probably) unique message ID
     -- We could do other things to guarantee uniqueness, but we really don't need to
     -- Store it to ensure we don't get our own messages back
@@ -93,6 +99,9 @@ function send( nRecipient, message, sProtocol )
 end
 
 function broadcast( message, sProtocol )
+    if sProtocol ~= nil and type( sProtocol ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( sProtocol ) .. ")", 2 )
+    end
     send( CHANNEL_BROADCAST, message, sProtocol )
 end
 
@@ -101,6 +110,12 @@ function receive( sProtocolFilter, nTimeout )
     if type(sProtocolFilter) == "number" and nTimeout == nil then
         sProtocolFilter, nTimeout = nil, sProtocolFilter
     end
+    if sProtocolFilter ~= nil and type( sProtocolFilter ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sProtocolFilter ) .. ")", 2 )
+    end
+    if nTimeout ~= nil and type( nTimeoutl ) ~= "number" then
+        error( "bad argument #2 (expected number, got " .. type( nTimeout ) .. ")", 2 )
+    end
 
     -- Start the timer
     local timer = nil
@@ -131,8 +146,11 @@ function receive( sProtocolFilter, nTimeout )
 end
 
 function host( sProtocol, sHostname )
-    if type( sProtocol ) ~= "string" or type( sHostname ) ~= "string" then
-        error( "expected string, string", 2 )
+    if type( sProtocol ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sProtocol ) .. ")", 2 )
+    end
+    if type( sHostname ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( sHostname ) .. ")", 2 )
     end
     if sHostname == "localhost" then
         error( "Reserved hostname", 2 )
@@ -147,14 +165,17 @@ end
 
 function unhost( sProtocol )
     if type( sProtocol ) ~= "string" then
-        error( "expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sProtocol ) .. ")", 2 )
     end
     tHostnames[ sProtocol ] = nil
 end
 
 function lookup( sProtocol, sHostname )
     if type( sProtocol ) ~= "string" then
-        error( "expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sProtocol ) .. ")", 2 )
+    end
+    if sHostname ~= nil and type( sHostname ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( sHostname ) .. ")", 2 )
     end
 
     -- Build list of host IDs