diff --git a/README.md b/README.md
index 6a50cf50..60631840 100644
--- a/README.md
+++ b/README.md
@@ -387,7 +387,7 @@ Streamline also provides _stream wrappers_ that simplify stream programming. The
 
 You can seamlessly debug streamline code thanks to [JavaScript source maps](http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/). See [this video](https://www.youtube.com/watch?v=duC1Sqy66IE) for a quick demo.
 
-To activate this feature, pass the `--source-map` options to `_node` or `_coffee`, or set the `sourcemap` option if you register via a loader.
+To activate this feature, pass the `--source-map` options to `_node` or `_coffee`, or set the `sourceMap` option if you register via a loader.
 
 <a name="flamegraph">
 # Monitoring performance with flame graphs
@@ -460,7 +460,7 @@ For support and discussion, please join the [streamline.js mailing list](http://
 
 See the [AUTHORS](https://github.com/Sage/streamlinejs/blob/master/AUTHORS) file.
 
-Special thanks to Marcel Laverdet who contributed the _fibers_ implementation and to Geoffry Song who contributed sourcemap support.
+Special thanks to Marcel Laverdet who contributed the _fibers_ implementation and to Geoffry Song who contributed source map support.
 
 <a name="license">
 # License
diff --git a/lib/callbacks/transform.js b/lib/callbacks/transform.js
index fff3fb47..b4eb0dd5 100644
--- a/lib/callbacks/transform.js
+++ b/lib/callbacks/transform.js
@@ -276,6 +276,7 @@ if (typeof exports !== 'undefined') {
 						return child;
 					}, true);
 					node = _flatten(node);
+					node.loc = node.loc || loc;
 					return node;
 				}
 			}
@@ -1881,6 +1882,7 @@ if (typeof exports !== 'undefined') {
 			var node = esprima.parse(source, {
 				loc: true,
 				range: true,
+				source: options.sourceName || '<unknown>',
 			});
 			node = node.body[0].body;
 			if (node.type !== 'BlockStatement') throw new Error("source wrapper error: " + node.type);
@@ -1904,22 +1906,38 @@ if (typeof exports !== 'undefined') {
 			var used = {};
 			node = _simplify(node, options, used);
 			//fixRanges(node);
-			addNewlines(node);
-			var result = escodegen.generate(node, {
+			if (options.lines === "preserve") addNewlines(node);
+
+			// transform top node into Program to avoid extra curly braces
+			if (node.type === "BlockStatement") node.type = "Program";
+
+			var ecopts = options.sourceMap ? {
+				sourceMap: true,
+				sourceMapWithCode: true,
+			} : options.lines === "preserve" ? {
 				comment: true,
-			});
-			// remove curly braces around generated source
-			result = result[0] === '{' ? result.substring(1, result.length - 1) : result;
-			// turn comments into newlines
-			//result = result.replace(/\n\s*/g, ' ').replace(/\/\*undefined\*\//g, '\n');
-			result = result.split(/\/\*undefined\*\/\n/).map(function(s) {
-				return s.replace(/\n\s*/g, ' ');
-			}).join('\n');
+			} : {};
+			var result = escodegen.generate(node, ecopts);
+			if (options.sourceMap) {
+				// convert result into a SourceNode.
+				// would be much easier (and faster) if escodegen had an option to return SourceNode directly 
+				var SourceNode = require('source-map').SourceNode;
+				var SourceMapConsumer = require('source-map').SourceMapConsumer;
+				result = SourceNode.fromStringWithSourceMap(result.code, new SourceMapConsumer(result.map.toString()));
+			}
+
+			if (options.lines === "preserve") {
+				// turn comments into newlines
+				//result = result.replace(/\n\s*/g, ' ').replace(/\/\*undefined\*\//g, '\n');
+				result = result.split(/\/\*undefined\*\/\n/).map(function(s) {
+					return s.replace(/\n\s*/g, ' ');
+				}).join('\n');
+			};
 
 			// add helpers at beginning so that __g is initialized before any other code
 			if (!options.noHelpers) {
 				var s = exports.helpersSource(options, used, strict);
-				if (options.lines == "sourcemap") {
+				if (options.sourceMap) {
 					result.prepend(s);
 				} else {
 					result = s + result;
diff --git a/lib/compiler/compile._js b/lib/compiler/compile._js
index 0153eb30..69b4de4f 100644
--- a/lib/compiler/compile._js
+++ b/lib/compiler/compile._js
@@ -113,12 +113,13 @@ function outputFile(_, inFile, options) {
 }
 
 function fixSourceMap(sourceMap) {
-	var keys = {};
+	var prev;
 	sourceMap._mappings._array = sourceMap._mappings._array.filter(function(mapping) {
 		if (!mapping.originalLine) return false;
-		var key = mapping.originalLine + '/' + mapping.originalColumn;
-		if (keys[key]) return false;
-		keys[key] = true;
+		if (prev && mapping.source === prev.source //
+			&& mapping.originalLine === prev.originalLine //
+			&& mapping.originalColumn === prev.originalColumn) return false;
+		prev = mapping;
 		return true;
 	});
 }
@@ -315,7 +316,7 @@ function cachedTransform(_, content, path, transform, banner, options) {
 	}
 	// no luck in cache
 	if (options.verbose) console.log("streamline: transforming: " + path);
-	options.lines = options.lines || "sourcemap";
+	options.lines = options.lines || (options.sourceMap ? "sourcemap" : "preserve");
 	transformed = banner + _transform(transform, content, options);
 	if (options.cache && path.indexOf('/tmp--') < 0) fs.writeFile(f, transformed, "utf8", ~_);
 	return transformed;
diff --git a/lib/compiler/compileSync.js b/lib/compiler/compileSync.js
index e25bf779..750e2981 100644
--- a/lib/compiler/compileSync.js
+++ b/lib/compiler/compileSync.js
@@ -154,7 +154,7 @@ function cachedTransformSync(content, path, transform, banner, options, testOnly
 		r[k] = options[k];
 		return r;
 	}, {});
-	opts.lines = opts.lines || "sourcemap";
+	opts.lines = opts.lines || (opts.sourceMap ? "sourcemap" : "preserve");
 	transformed = banner + _transform(transform, content, opts);
 	if (options.cache && path.indexOf('/tmp--') < 0) fs.writeFileSync(f, transformed, "utf8");
 	return transformed;