diff --git a/services/web/app/coffee/Features/Compile/ClsiManager.coffee b/services/web/app/coffee/Features/Compile/ClsiManager.coffee
index cff2b931b6..c27bc2fe90 100755
--- a/services/web/app/coffee/Features/Compile/ClsiManager.coffee
+++ b/services/web/app/coffee/Features/Compile/ClsiManager.coffee
@@ -29,7 +29,11 @@ module.exports = ClsiManager =
 
 	sendRequestOnce: (project_id, user_id, options = {}, callback = (error, status, outputFiles, clsiServerId, validationProblems) ->) ->
 		ClsiManager._buildRequest project_id, options, (error, req) ->
-			return callback(error) if error?
+			if error?
+				if error.message is "no main file specified"
+					return callback(null, "validation-problems", null, null, {mainFile:error.message})
+				else
+					return callback(error)
 			logger.log project_id: project_id, "sending compile to CLSI"
 			ClsiFormatChecker.checkRecoursesForProblems req.compile?.resources, (err, validationProblems)->
 				if err?
@@ -180,7 +184,7 @@ module.exports = ClsiManager =
 				# present in the docupdater. This allows finaliseRequest to
 				# identify the root doc.
 				possibleRootDocIds = [options.rootDoc_id, project.rootDoc_id]
-				for rootDoc_id in possibleRootDocIds when rootDoc_id?
+				for rootDoc_id in possibleRootDocIds when rootDoc_id? and rootDoc_id of docPath
 					path = docPath[rootDoc_id]
 					docs[path] ?= {_id: rootDoc_id, path: path}
 				ClsiManager._finaliseRequest project_id, options, project, docs, [], callback
@@ -206,9 +210,12 @@ module.exports = ClsiManager =
 		resources = []
 		rootResourcePath = null
 		rootResourcePathOverride = null
+		hasMainFile = false
+		numberOfDocsInProject = 0
 
 		for path, doc of docs
 			path = path.replace(/^\//, "") # Remove leading /
+			numberOfDocsInProject++
 			if doc.lines? # add doc to resources unless it is just a stub entry
 				resources.push
 					path:    path
@@ -217,11 +224,20 @@ module.exports = ClsiManager =
 				rootResourcePath = path
 			if options.rootDoc_id? and doc._id.toString() == options.rootDoc_id.toString()
 				rootResourcePathOverride = path
+			if path is "main.tex"
+				hasMainFile = true
 
 		rootResourcePath = rootResourcePathOverride if rootResourcePathOverride?
 		if !rootResourcePath?
-			logger.warn {project_id}, "no root document found, setting to main.tex"
-			rootResourcePath = "main.tex"
+			if hasMainFile
+				logger.warn {project_id}, "no root document found, setting to main.tex"
+				rootResourcePath = "main.tex"
+			else if numberOfDocsInProject is 1 # only one file, must be the main document
+				for path, doc of docs
+					rootResourcePath = path.replace(/^\//, "") # Remove leading /
+				logger.warn {project_id, rootResourcePath: rootResourcePath}, "no root document found, single document in project"
+			else
+				return callback new Error("no main file specified")
 
 		for path, file of files
 			path = path.replace(/^\//, "") # Remove leading /
diff --git a/services/web/app/views/project/editor/pdf.pug b/services/web/app/views/project/editor/pdf.pug
index 58b0aa6521..429fa41c6f 100644
--- a/services/web/app/views/project/editor/pdf.pug
+++ b/services/web/app/views/project/editor/pdf.pug
@@ -317,6 +317,9 @@ div.full-size.pdf(ng-controller="PdfController")
 				div
 					li(ng-repeat="entry in pdf.validation.conflictedPaths") {{ '/'+entry['path'] }}
 
+			.alert.alert-danger(ng-show="pdf.validation.mainFile")
+				strong #{translate("main_file_not_found")} 
+				span #{translate("please_set_main_file")}
 
 		.pdf-errors(ng-switch-when="errors")
 	
diff --git a/services/web/public/coffee/ide/pdf/controllers/PdfController.coffee b/services/web/public/coffee/ide/pdf/controllers/PdfController.coffee
index 640c224e7b..4846837856 100644
--- a/services/web/public/coffee/ide/pdf/controllers/PdfController.coffee
+++ b/services/web/public/coffee/ide/pdf/controllers/PdfController.coffee
@@ -231,6 +231,7 @@ define [
 			else if response.status == "validation-problems"
 				$scope.pdf.view = "validation-problems"
 				$scope.pdf.validation = response.validationProblems
+				$scope.shouldShowLogs = false
 			else if response.status == "compile-in-progress"
 				$scope.pdf.view = 'errors'
 				$scope.pdf.compileInProgress = true
diff --git a/services/web/test/UnitTests/coffee/Compile/ClsiManagerTests.coffee b/services/web/test/UnitTests/coffee/Compile/ClsiManagerTests.coffee
index 6786c3a1a8..bd02af2f28 100644
--- a/services/web/test/UnitTests/coffee/Compile/ClsiManagerTests.coffee
+++ b/services/web/test/UnitTests/coffee/Compile/ClsiManagerTests.coffee
@@ -346,7 +346,49 @@ describe "ClsiManager", ->
 
 			it "should set to main.tex", ->
 				@request.compile.rootResourcePath.should.equal "main.tex"
-		
+
+		describe "when there is no valid root document and no main.tex document", ->
+			beforeEach () ->
+				@project.rootDoc_id = "not-valid"
+				@docs = {
+					"/other.tex": @doc_1 = {
+						name: "other.tex"
+						_id: "mock-doc-id-1"
+						lines: ["Hello", "world"]
+					},
+					"/chapters/chapter1.tex": @doc_2 = {
+						name: "chapter1.tex"
+						_id: "mock-doc-id-2"
+						lines: [
+							"Chapter 1"
+						]
+					}
+				}
+				@ProjectEntityHandler.getAllDocs = sinon.stub().callsArgWith(1, null, @docs)
+				@ClsiManager._buildRequest @project, null, @callback
+
+			it "should report an error", ->
+				@callback.calledWith(new Error("no main file specified")).should.equal true
+
+
+		describe "when there is no valid root document and a single document which is not main.tex", ->
+			beforeEach (done) ->
+				@project.rootDoc_id = "not-valid"
+				@docs = {
+					"/other.tex": @doc_1 = {
+						name: "other.tex"
+						_id: "mock-doc-id-1"
+						lines: ["Hello", "world"]
+					}
+				}
+				@ProjectEntityHandler.getAllDocs = sinon.stub().callsArgWith(1, null, @docs)
+				@ClsiManager._buildRequest @project, null, (@error, @request) =>
+					done()
+
+			it "should set io to the only file", ->
+				@request.compile.rootResourcePath.should.equal "other.tex"
+
+
 		describe "with the draft option", ->
 			it "should add the draft option into the request", (done) ->
 				@ClsiManager._buildRequest @project_id, {timeout:100, draft: true}, (error, request) =>