diff --git a/index.html b/index.html
index 1ce84a6d79..2aa4baf3d6 100644
--- a/index.html
+++ b/index.html
@@ -512,7 +512,7 @@
 
 			var previousInput = '';
 			var sourceAnnotations = [];
-			var compile = function() {
+			var compile = function(missingInputs) {
 				editor.getSession().clearAnnotations();
 				sourceAnnotations = [];
 				editor.getSession().removeMarker(errMarkerId);
@@ -522,13 +522,17 @@
 
 				var files = {};
 				files[fileNameFromKey(SOL_CACHE_FILE)] = input;
-				var input = gatherImports(files, compile);
-				if (!input) return;
-				var optimize = document.querySelector('#optimize').checked;
-
-				compileJSON(input, optimize ? 1 : 0);
+				gatherImports(files, missingInputs, function(input, error) {
+					$('#output').empty();
+					if (input === null) {
+						renderError(error);
+					} else {
+						var optimize = document.querySelector('#optimize').checked;
+						compileJSON(input, optimize ? 1 : 0);
+					}
+				});
 			};
-			var compilationFinished = function(result) {
+			var compilationFinished = function(result, missingInputs) {
 				var data = $.parseJSON(result);
 				var noFatalErrors = true; // ie warnings are ok
 
@@ -543,7 +547,10 @@
 					});
 				}
 			
-				if (noFatalErrors && !hidingRHP) renderContracts(data, editor.getValue());
+				if (missingInputs !== undefined && missingInputs.length > 0)
+					compile(missingInputs);
+				else if (noFatalErrors && !hidingRHP)
+					renderContracts(data, editor.getValue());
 			};
 			
 			var compileTimeout = null;
@@ -563,7 +570,18 @@
 			var onCompilerLoaded = function() {
 				if (worker === null) {
 					var compile;
-					if ('_compileJSONMulti' in Module) {
+					var missingInputs = [];
+					if ('_compileJSONCallback' in Module) {
+						compilerAcceptsMultipleFiles = true;
+						var missingInputsCallback = Module.Runtime.addFunction(function(path, contents, error) {
+							missingInputs.push(Module.Pointer_stringify(path));
+						});
+						var compileInternal = Module.cwrap("compileJSONCallback", "string", ["string", "number", "number"]);
+						compile = function(input, optimize) {
+							missingInputs.length = 0;
+							return compileInternal(input, optimize, missingInputsCallback);
+						};
+					} else if ('_compileJSONMulti' in Module) {
 						compilerAcceptsMultipleFiles = true;
 						compile = Module.cwrap("compileJSONMulti", "string", ["string", "number"]);
 					} else {
@@ -576,7 +594,7 @@
 						} catch (exception) {
 							result = JSON.stringify({error: 'Uncaught JavaScript exception:\n' + exception});
 						}
-						compilationFinished(result);
+						compilationFinished(result, missingInputs);
 					};
 					$('#version').text(Module.cwrap("version", "string", [])());
 				}
@@ -585,49 +603,54 @@
 			};
 
 			var cachedRemoteFiles = {};
-			function gatherImports(files, asyncCallback, needAsync) {
+			function gatherImports(files, importHints, cb) {
+				importHints = importHints || [];
 				if (!compilerAcceptsMultipleFiles)
-					return files[fileNameFromKey(SOL_CACHE_FILE)];
+				{
+					cb(files[fileNameFromKey(SOL_CACHE_FILE)]);
+					return;
+				}
 				var importRegex = /import\s[\'\"]([^\'\"]+)[\'\"];/g;
 				var reloop = false;
 				do {
 					reloop = false;
 					for (var fileName in files) {
 						var match;
-						while (match = importRegex.exec(files[fileName])) {
-							var m = match[1];
-							if (m in files) continue;
-							if (getFiles().indexOf(fileKey(m)) !== -1) {
-								files[m] = window.localStorage[fileKey(match[1])];
-								reloop = true;
-							} else if (m in cachedRemoteFiles) {
-								files[m] = cachedRemoteFiles[m];
-								reloop = true;
-							} else if (githubMatch = /^(https?:\/\/)?(www.)?github.com\/([^\/]*\/[^\/]*)\/(.*)/.exec(m)) {
-								$.getJSON('https://api.github.com/repos/' + githubMatch[3] + '/contents/' + githubMatch[4], function(result) {
-									var content;
-									if ('content' in result)
-										content = Base64.decode(result.content);
-									else
-										content = "\"" + m + "\" NOT FOUND"; //@TODO handle this better
-									cachedRemoteFiles[m] = content;
-									files[m] = content;
-									gatherImports(files, asyncCallback, true);
-								}).fail(function(){
-									var content = "\"" + m + "\" NOT FOUND"; //@TODO handle this better
+						while (match = importRegex.exec(files[fileName]))
+							importHints.push(match[1]);
+					}
+					while (importHints.length > 0) {
+						var m = importHints.pop();
+						if (m in files) continue;
+						if (getFiles().indexOf(fileKey(m)) !== -1) {
+							files[m] = window.localStorage[fileKey(m)];
+							reloop = true;
+						} else if (m in cachedRemoteFiles) {
+							files[m] = cachedRemoteFiles[m];
+							reloop = true;
+						} else if (githubMatch = /^(https?:\/\/)?(www.)?github.com\/([^\/]*\/[^\/]*)\/(.*)/.exec(m)) {
+							$('#output').append($('<div/>').append($('<pre/>').text("Loading github.com/" + githubMatch[3] + " ...")));
+							$.getJSON('https://api.github.com/repos/' + githubMatch[3] + '/contents/' + githubMatch[4], function(result) {
+								if ('content' in result)
+								{
+									var content = Base64.decode(result.content);
 									cachedRemoteFiles[m] = content;
 									files[m] = content;
-									gatherImports(files, asyncCallback, true);
-								});
-								return null;
-							}
+									gatherImports(files, importHints, cb);
+								}
+								else
+									cb(null, "Unable to import \"" + m + "\"");
+							}).fail(function(){
+								cb(null, "Unable to import \"" + m + "\"");
+							});
+							return;
+						} else {
+							cb(null, "Unable to import \"" + m + "\"");
+							return;
 						}
 					}
 				} while (reloop);
-				var input = JSON.stringify({'sources':files});
-				if (needAsync)
-					asyncCallback(input);
-				return input;
+				cb(JSON.stringify({'sources':files}));
 			}
 
 			var initializeWorker = function() {
@@ -643,7 +666,7 @@
 						onCompilerLoaded();
 						break;
 					case 'compiled':
-						compilationFinished(data.data);
+						compilationFinished(data.data, data.missingInputs);
 						break;
 					};
 				});
diff --git a/index.js b/index.js
index ed5f2a7d3b..4e4c14f88d 100644
--- a/index.js
+++ b/index.js
@@ -5,9 +5,42 @@ function setupMethods (soljson){
 		'_compileJSONMulti' in soljson ?
 		soljson.cwrap("compileJSONMulti", "string", ["string", "number"]) :
 		null;
+	var compileJSONCallback = null;
+	if ('_compileJSONCallback' in soljson)
+	{
+		/// TODO: Allocating memory and copying the strings over
+		/// to the emscripten runtime does not seem to work.
+		var copyString = function(str, ptr) {
+			var buffer = soljson._malloc(str.length + 1);
+			soljson.writeStringToMemory(str, buffer);
+			soljson.setValue(ptr, buffer, '*');
+		};
+		var wrapCallback = function(callback) {
+			return soljson.Runtime.addFunction(function(path, contents, error) {
+				// path is char*, contents is char**, error is char**
+				// TODO copying the results does not seem to work.
+				// This is not too bad, because most of the requests
+				// cannot be answered synchronously anyway.
+				var result = callback(soljson.Pointer_stringify(path));
+				if (typeof(result.contents) === typeof(''))
+					copyString(result.contents, contents);
+				if (typeof(result.error) === typeof(''))
+					copyString(result.error, error);
+			});
+		};
+		var compileInternal = soljson.cwrap("compileJSONCallback", "string", ["string", "number", "number"]);
+		compileJSONCallback = function(input, optimize, readCallback) {
+			var cb = wrapCallback(readCallback);
+			var output = compileInternal(input, optimize, cb);
+			soljson.Runtime.removeFunction(cb);
+			return output;
+		};
+	}
 
-	var compile = function(input, optimise) {
+	var compile = function(input, optimise, readCallback) {
 		var result = '';
+		if (readCallback !== undefined && compileJSONCallback !== null)
+			result = compileJSONCallback(JSON.stringify(input), optimise, readCallback);
 		if (typeof(input) != typeof('') && compileJSONMulti !== null)
 			result = compileJSONMulti(JSON.stringify(input), optimise);
 		else
diff --git a/worker.js b/worker.js
index 2edea48ff7..1a1c714c97 100644
--- a/worker.js
+++ b/worker.js
@@ -2,6 +2,7 @@ var version = function() { return '(loading)'; }
 var compileJSON = function() { return ''; }
 addEventListener('message', function(e) {
 	var data = e.data;
+	var missingInputs = [];
 	switch (data.cmd) {
 		case 'loadVersion':
 			delete Module;
@@ -10,7 +11,17 @@ addEventListener('message', function(e) {
 
 			importScripts(data.data);
 			version = Module.cwrap("version", "string", []);
-			if ('_compileJSONMulti' in Module)
+			if ('_compileJSONCallback' in Module)
+			{
+				compileJSONInternal = Module.cwrap("compileJSONCallback", "string", ["string", "number", "number"]);
+				var missingInputCallback = Module.Runtime.addFunction(function(path) {
+					missingInputs.push(Module.Pointer_stringify(path));
+				});
+				compileJSON = function(input, optimize) {
+					return compileJSONInternal(input, optimize, missingInputCallback);
+				};
+			}
+			else if ('_compileJSONMulti' in Module)
 				compileJSON = Module.cwrap("compileJSONMulti", "string", ["string", "number"]);
 			else
 				compileJSON = Module.cwrap("compileJSON", "string", ["string", "number"]);
@@ -21,7 +32,8 @@ addEventListener('message', function(e) {
 			});
 			break;
 		case 'compile':
-			postMessage({cmd: 'compiled', data: compileJSON(data.source, data.optimize)});
+			missingInputs
+			postMessage({cmd: 'compiled', data: compileJSON(data.source, data.optimize)}, missingInputs: missingInputs);
 			break;
 	}
 }, false);