diff --git a/src/core/org/luaj/vm2/LuaString.java b/src/core/org/luaj/vm2/LuaString.java
index 5ff8a97e..e28d8202 100644
--- a/src/core/org/luaj/vm2/LuaString.java
+++ b/src/core/org/luaj/vm2/LuaString.java
@@ -388,7 +388,7 @@ public class LuaString extends LuaValue {
 	public static String decodeAsUtf8(byte[] bytes, int offset, int length) {
 		int i,j,n,b;
 		for ( i=offset,j=offset+length,n=0; i<j; ++n ) {
-			switch ( 0xC0 & bytes[i++] ) {
+			switch ( 0xE0 & bytes[i++] ) {
 			case 0xE0: ++i;
 			case 0xC0: ++i;
 			}
diff --git a/src/core/org/luaj/vm2/LuaValue.java b/src/core/org/luaj/vm2/LuaValue.java
index 51fc1d24..f8727588 100644
--- a/src/core/org/luaj/vm2/LuaValue.java
+++ b/src/core/org/luaj/vm2/LuaValue.java
@@ -118,40 +118,40 @@ public class LuaValue extends Varargs {
 	public LuaValue    tostring()     { return NIL; }
 
 	// optional argument conversions
-	public boolean     optboolean(boolean defval)          { typerror("boolean");   return false; }
-	public LuaClosure  optclosure(LuaClosure defval)       { typerror("closure");   return null;  }
-	public double      optdouble(double defval)            { typerror("double");    return 0;     }
-	public LuaFunction optfunction(LuaFunction defval)     { typerror("function");  return null;  }
-	public int         optint(int defval)                  { typerror("int");       return 0;     }
-	public LuaInteger  optinteger(LuaInteger defval)       { typerror("integer");   return null;  }
-	public long        optlong(long defval)                { typerror("long");      return 0;     }
-	public LuaNumber   optnumber(LuaNumber defval)         { typerror("number");    return null;  }
-	public String      optjstring(String defval)           { typerror("String");    return null;  }
-	public LuaString   optstring(LuaString defval)         { typerror("string");    return null;  }
-	public LuaTable    opttable(LuaTable defval)           { typerror("table");     return null;  }
-	public LuaThread   optthread(LuaThread defval)         { typerror("thread");    return null;  }
-	public Object      optuserdata(Object defval)          { typerror("object");    return null;  }
-	public Object      optuserdata(Class c, Object defval) { typerror(c.getName()); return null;  }
+	public boolean     optboolean(boolean defval)          { argerror("boolean");   return false; }
+	public LuaClosure  optclosure(LuaClosure defval)       { argerror("closure");   return null;  }
+	public double      optdouble(double defval)            { argerror("double");    return 0;     }
+	public LuaFunction optfunction(LuaFunction defval)     { argerror("function");  return null;  }
+	public int         optint(int defval)                  { argerror("int");       return 0;     }
+	public LuaInteger  optinteger(LuaInteger defval)       { argerror("integer");   return null;  }
+	public long        optlong(long defval)                { argerror("long");      return 0;     }
+	public LuaNumber   optnumber(LuaNumber defval)         { argerror("number");    return null;  }
+	public String      optjstring(String defval)           { argerror("String");    return null;  }
+	public LuaString   optstring(LuaString defval)         { argerror("string");    return null;  }
+	public LuaTable    opttable(LuaTable defval)           { argerror("table");     return null;  }
+	public LuaThread   optthread(LuaThread defval)         { argerror("thread");    return null;  }
+	public Object      optuserdata(Object defval)          { argerror("object");    return null;  }
+	public Object      optuserdata(Class c, Object defval) { argerror(c.getName()); return null;  }
 	public LuaValue    optvalue(LuaValue defval)           { return this; }
 
 	/** @deprecated - use optjstring() instead */
 	public String      optString(String defval)            { return optjstring(defval);  }
 
 	// argument type checks
-	public boolean     checkboolean()          { typerror("boolean");   return false; }
-	public LuaClosure  checkclosure()          { typerror("closure");   return null;  }
-	public double      checkdouble()           { typerror("double");    return 0; }
-	public LuaValue    checkfunction()         { typerror("function");  return null; }	
-	public int         checkint()              { typerror("int");       return 0; }
-	public LuaInteger  checkinteger()          { typerror("integer");   return null; }
-	public long        checklong()             { typerror("long");      return 0; }
-	public LuaNumber   checknumber()           { typerror("number");    return null; }
-	public String      checkjstring()          { typerror("string");    return null; }
-	public LuaString   checkstring()           { typerror("string");    return null; }
-	public LuaTable    checktable()            { typerror("table");     return null; }	
-	public LuaThread   checkthread()           { typerror("thread");    return null; }
-	public Object      checkuserdata()         { typerror("userdata");  return null; }
-	public Object      checkuserdata(Class c)  { typerror("userdata");  return null; }
+	public boolean     checkboolean()          { argerror("boolean");   return false; }
+	public LuaClosure  checkclosure()          { argerror("closure");   return null;  }
+	public double      checkdouble()           { argerror("double");    return 0; }
+	public LuaValue    checkfunction()         { argerror("function");  return null; }	
+	public int         checkint()              { argerror("int");       return 0; }
+	public LuaInteger  checkinteger()          { argerror("integer");   return null; }
+	public long        checklong()             { argerror("long");      return 0; }
+	public LuaNumber   checknumber()           { argerror("number");    return null; }
+	public String      checkjstring()          { argerror("string");    return null; }
+	public LuaString   checkstring()           { argerror("string");    return null; }
+	public LuaTable    checktable()            { argerror("table");     return null; }	
+	public LuaThread   checkthread()           { argerror("thread");    return null; }
+	public Object      checkuserdata()         { argerror("userdata");  return null; }
+	public Object      checkuserdata(Class c)  { argerror("userdata");  return null; }
 	public LuaValue    checknotnil()           { return this; }
 	public LuaValue    checkvalidkey()         { return this; }
 
@@ -162,10 +162,12 @@ public class LuaValue extends Varargs {
 	// errors
 	public static LuaValue error(String message) { throw new LuaError(message); }
 	public static void assert_(boolean b,String msg) { if(!b) throw new LuaError(msg); }
+	protected LuaValue argerror(String expected) { throw new LuaError("bad argument: "+expected+" expected, got "+typename()); }
 	public static void argerror(int iarg,String msg) { throw new LuaError("bad argument #"+iarg+": "+msg); }
-	protected LuaValue typerror(String expected) { throw new LuaError("bad argument: "+expected+" expected, got "+typename()); }
-	protected LuaValue typerror(int iarg, String expected) { throw new LuaError("bad argument #"+iarg+": "+expected+" expected, got "+typename()); }
+	protected LuaValue typerror(String expected) { throw new LuaError(expected+" expected, got "+typename()); }
 	protected LuaValue unimplemented(String fun) { throw new LuaError("'"+fun+"' not implemented for "+typename()); }
+	protected LuaValue callerror() { throw new LuaError("attempt to call "+typename()); }
+	protected LuaValue lenerror() { throw new LuaError("attempt to get length of "+typename()); }
 	protected LuaValue aritherror() { throw new LuaError("attempt to perform arithmetic on "+typename()); }
 	protected LuaValue aritherror(String fun) { throw new LuaError("attempt to perform arithmetic '"+fun+"' on "+typename()); }
 	
@@ -208,10 +210,10 @@ public class LuaValue extends Varargs {
 	public void setfenv(LuaValue env) { typerror("function or thread"); }
 		
 	// function calls
-	public LuaValue call() { return unimplemented("call"); }
-	public LuaValue call(LuaValue arg) { return unimplemented("call"); }
-	public LuaValue call(LuaValue arg1, LuaValue arg2) { return unimplemented("call"); }
-	public LuaValue call(LuaValue arg1, LuaValue arg2, LuaValue arg3) { return unimplemented("call"); }
+	public LuaValue call() { return callerror(); }
+	public LuaValue call(LuaValue arg) { return callerror(); }
+	public LuaValue call(LuaValue arg1, LuaValue arg2) { return callerror(); }
+	public LuaValue call(LuaValue arg1, LuaValue arg2, LuaValue arg3) { return callerror(); }
 	public LuaValue method(String name) { return this.get(name).call(this); }
 	public LuaValue method(LuaValue name) { return this.get(name).call(this); }
 	public LuaValue method(String name, LuaValue arg) { return this.get(name).call(this,arg); }
@@ -219,7 +221,7 @@ public class LuaValue extends Varargs {
 	public LuaValue method(String name, LuaValue arg1, LuaValue arg2) { return this.get(name).call(this,arg1,arg2); }
 	public LuaValue method(LuaValue name, LuaValue arg1, LuaValue arg2) { return this.get(name).call(this,arg1,arg2); }
 	public Varargs invoke() { return invoke(NONE); }
-	public Varargs invoke(Varargs args) { unimplemented("call"); return null; }
+	public Varargs invoke(Varargs args) { return callerror(); }
 	public Varargs invoke(LuaValue arg,Varargs varargs) { return invoke(varargsOf(arg,varargs)); }
 	public Varargs invoke(LuaValue arg1,LuaValue arg2,Varargs varargs) { return invoke(varargsOf(arg1,arg2,varargs)); }
 	public Varargs invoke(LuaValue[] args) { return invoke(varargsOf(args)); }
@@ -232,8 +234,8 @@ public class LuaValue extends Varargs {
 	// unary operators
 	public LuaValue not()  { return FALSE;  }
 	public LuaValue neg()  { return aritherror("neg");  }
-	public LuaValue len()  { return typerror("len");  }
-	public int length() { typerror("len"); return 0; }
+	public LuaValue len()  { return lenerror(); }
+	public int length() { error("attempt to get length of "+typename()); return 0; }
 	public LuaValue getn() { return typerror("getn"); }
 	
 	// object equality, used for key comparison
@@ -287,8 +289,8 @@ public class LuaValue extends Varargs {
 	public boolean gteq_b( double rhs )    { aritherror("gteq"); return false; }
 
 	// string comparison
-	public int strcmp( LuaValue rhs )         { typerror("attempt to compare "+typename()); return 0; }
-	public int strcmp( LuaString rhs )      { typerror("attempt to compare "+typename()); return 0; }
+	public int strcmp( LuaValue rhs )         { error("attempt to compare "+typename()); return 0; }
+	public int strcmp( LuaString rhs )      { error("attempt to compare "+typename()); return 0; }
 
 	// concatenation
 	public LuaValue   concat( LuaValue rhs )      { return valueOf(concat_s(rhs)); }
diff --git a/src/core/org/luaj/vm2/lib/BaseLib.java b/src/core/org/luaj/vm2/lib/BaseLib.java
index 8e0b40e0..29a2b7a2 100644
--- a/src/core/org/luaj/vm2/lib/BaseLib.java
+++ b/src/core/org/luaj/vm2/lib/BaseLib.java
@@ -276,7 +276,7 @@ public class BaseLib extends OneArgFunction implements ResourceFinder {
 					return valueOf(n);
 				int i = args.checkint(1);
 				if ( i == 0 || i < -n )
-					typerror(1,"index out of range");
+					argerror(1,"index out of range");
 				return args.subargs(i<0? n+i+2: i+1);
 			}
 			case 9: // "unpack", // (list [,i [,j]]) -> result1, ...
diff --git a/src/core/org/luaj/vm2/lib/IoLib.java b/src/core/org/luaj/vm2/lib/IoLib.java
index 119f96ab..b6226841 100644
--- a/src/core/org/luaj/vm2/lib/IoLib.java
+++ b/src/core/org/luaj/vm2/lib/IoLib.java
@@ -444,7 +444,7 @@ public class IoLib extends OneArgFunction {
 				else if ( "*l".equals(format) )
 					v[i] = freadline(f);
 				else
-					typerror( i+1, "(invalid format)" );
+					argerror( i+1, "(invalid format)" );
 			}
 			if ( v[i].isnil() )
 				return i==0? NIL: varargsOf(v,0,i);
diff --git a/test/junit/org/luaj/vm2/StringTest.java b/test/junit/org/luaj/vm2/StringTest.java
index 4e034f9e..a158679b 100644
--- a/test/junit/org/luaj/vm2/StringTest.java
+++ b/test/junit/org/luaj/vm2/StringTest.java
@@ -66,6 +66,16 @@ public class StringTest extends TestCase {
 		}
 		return sb.toString();
 	}
+
+	public void testUtf820482051() throws UnsupportedEncodingException {
+		int i = 2048;
+		char[] c = { (char) (i+0), (char) (i+1), (char) (i+2), (char) (i+3) };
+		String before = new String(c)+" "+i+"-"+(i+4);
+		LuaString ls = LuaString.valueOf(before);
+		String after = ls.tojstring();
+		assertEquals( userFriendly( before ), userFriendly( after ) );
+		
+	}
 	
 	public void testUtf8() {		
 		for ( int i=4; i<0xffff; i+=4 ) {
@@ -101,7 +111,7 @@ public class StringTest extends TestCase {
 		String before = new String(c);
 		LuaString ls = LuaString.valueOf(before);
 		String after = ls.tojstring();
-		assertEquals( userFriendly( "abc" ), userFriendly( after ) );
+		assertEquals( userFriendly( "abc\0def" ), userFriendly( after ) );
 		
 	}
 }
diff --git a/test/lua/errors/operators.lua b/test/lua/errors/operators.lua
index 9633ef19..5a69b8d4 100644
--- a/test/lua/errors/operators.lua
+++ b/test/lua/errors/operators.lua
@@ -9,7 +9,7 @@ require 'args'
 banner('unary -')
 negative = function(a) return - a end
 checkallpass('negative',{somenumber})
-checkallerrors('negative',{notanumber},'attempt to perform arithmetic on')
+checkallerrors('negative',{notanumber},'attempt to perform arithmetic')
 
 -- length
 banner('#')
@@ -21,7 +21,7 @@ checkallerrors('lengthop',{notatable},'attempt to get length of')
 banner('not')
 notop = function(a) return not a end
 checkallpass('notop',{somenumber})
-checkallerrors('notop',{notanumber},'attempt to perform arithmetic on')
+checkallpass('notop',{notanumber})
 
 -- function call
 banner( '()' )