diff --git a/src/harness/unittests/cachingInServerLSHost.ts b/src/harness/unittests/cachingInServerLSHost.ts
index 19ec12d7c5b..74972d23d96 100644
--- a/src/harness/unittests/cachingInServerLSHost.ts
+++ b/src/harness/unittests/cachingInServerLSHost.ts
@@ -63,7 +63,7 @@ namespace ts {
         const projectService = new server.ProjectService(svcOpts);
         const rootScriptInfo = projectService.getOrCreateScriptInfo(rootFile, /* openedByClient */ true, /*containingProject*/ undefined);
 
-        const project = projectService.assignScriptInfoToInferredProject(rootScriptInfo);
+        const project = projectService.assignOrphanScriptInfoToInferredProject(rootScriptInfo);
         project.setCompilerOptions({ module: ts.ModuleKind.AMD, noLib: true } );
         return {
             project,
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 8abec41de41..20fc4cb8a58 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -202,7 +202,7 @@ namespace ts.projectSystem {
             typingsInstaller: undefined,
             byteLength: Utils.byteLength,
             hrtime: process.hrtime,
-            logger: nullLogger,
+            logger: opts.logger || nullLogger,
             canUseEvents: false
         };
 
@@ -2634,6 +2634,47 @@ namespace ts.projectSystem {
             checkNumberOfProjects(projectService, { configuredProjects: 0, externalProjects: 1, inferredProjects: 0 });
             checkProjectActualFiles(projectService.externalProjects[0], [site.path, libFile.path]);
         });
+
+        it("Getting errors from closed script info does not throw exception (because of getting project from orphan script info)", () => {
+            let hasErrorMsg = false;
+            const { close, hasLevel, loggingEnabled, info, group, perftrc, getLogFileName } = nullLogger;
+            const logger: server.Logger = {
+                close, hasLevel, loggingEnabled, info, group, perftrc, getLogFileName,
+                err: () => {
+                    hasErrorMsg = true;
+                }
+            };
+            const f1 = {
+                path: "/a/b/app.ts",
+                content: "let x = 1;"
+            };
+            const config = {
+                path: "/a/b/tsconfig.json",
+                content: JSON.stringify({ compilerOptions: {} })
+            };
+            const host = createServerHost([f1, libFile, config]);
+            const session = createSession(host, { logger });
+            session.executeCommandSeq(<protocol.OpenRequest>{
+                command: server.CommandNames.Open,
+                arguments: {
+                    file: f1.path
+                }
+            });
+            session.executeCommandSeq(<protocol.CloseRequest>{
+                command: server.CommandNames.Close,
+                arguments: {
+                    file: f1.path
+                }
+            });
+            session.executeCommandSeq(<protocol.GeterrRequest>{
+                command: server.CommandNames.Geterr,
+                arguments: {
+                    delay: 0,
+                    files: [f1.path]
+                }
+            });
+            assert.isFalse(hasErrorMsg);
+        });
     });
 
     describe("Proper errors", () => {
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 02e039ae88d..9f24f1ffa3f 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -564,7 +564,7 @@ namespace ts.server {
                 this.ensureProjectStructuresUptoDate();
             }
             const scriptInfo = this.getScriptInfoForNormalizedPath(fileName);
-            return scriptInfo && scriptInfo.getDefaultProject();
+            return scriptInfo && !scriptInfo.isOrphan() && scriptInfo.getDefaultProject();
         }
 
         /**
@@ -588,7 +588,7 @@ namespace ts.server {
                 else {
                     projectsToUpdate = [];
                     for (const f of this.changedFiles) {
-                        projectsToUpdate = projectsToUpdate.concat(f.containingProjects);
+                        addRange(projectsToUpdate, f.containingProjects);
                     }
                 }
                 this.changedFiles = undefined;
@@ -789,8 +789,8 @@ namespace ts.server {
         }
 
         /*@internal*/
-        assignScriptInfoToInferredProject(info: ScriptInfo, projectRootPath?: string) {
-            Debug.assert(info.containingProjects.length === 0);
+        assignOrphanScriptInfoToInferredProject(info: ScriptInfo, projectRootPath?: string) {
+            Debug.assert(info.isOrphan());
 
             const project = this.getOrCreateInferredProjectForProjectRootPathIfEnabled(info, projectRootPath) ||
                 this.getOrCreateSingleInferredProjectIfEnabled() ||
@@ -823,7 +823,7 @@ namespace ts.server {
         }
 
         private addToListOfOpenFiles(info: ScriptInfo) {
-            Debug.assert(info.containingProjects.length !== 0);
+            Debug.assert(!info.isOrphan());
             for (const p of info.containingProjects) {
                 // file is the part of configured project, addref the project
                 if (p.projectKind === ProjectKind.Configured) {
@@ -885,8 +885,8 @@ namespace ts.server {
 
                 // collect orphaned files and assign them to inferred project just like we treat open of a file
                 for (const f of this.openFiles) {
-                    if (f.containingProjects.length === 0) {
-                        this.assignScriptInfoToInferredProject(f);
+                    if (f.isOrphan()) {
+                        this.assignOrphanScriptInfoToInferredProject(f);
                     }
                 }
 
@@ -907,7 +907,7 @@ namespace ts.server {
 
         private deleteOrphanScriptInfoNotInAnyProject() {
             this.filenameToScriptInfo.forEach(info => {
-                if (!info.isScriptOpen() && info.containingProjects.length === 0) {
+                if (!info.isScriptOpen() && info.isOrphan()) {
                     // if there are not projects that include this script info - delete it
                     this.stopWatchingScriptInfo(info, WatcherCloseReason.OrphanScriptInfo);
                     this.filenameToScriptInfo.delete(info.path);
@@ -1809,8 +1809,8 @@ namespace ts.server {
 
             for (const info of this.openFiles) {
                 // collect all orphaned script infos from open files
-                if (info.containingProjects.length === 0) {
-                    this.assignScriptInfoToInferredProject(info);
+                if (info.isOrphan()) {
+                    this.assignOrphanScriptInfoToInferredProject(info);
                 }
                 else {
                     // Or remove the root of inferred project if is referenced in more than one projects
@@ -1867,8 +1867,8 @@ namespace ts.server {
 
             // At this point if file is part of any any configured or external project, then it would be present in the containing projects
             // So if it still doesnt have any containing projects, it needs to be part of inferred project
-            if (info.containingProjects.length === 0) {
-                this.assignScriptInfoToInferredProject(info, projectRootPath);
+            if (info.isOrphan()) {
+                this.assignOrphanScriptInfoToInferredProject(info, projectRootPath);
             }
             this.addToListOfOpenFiles(info);
 
diff --git a/src/server/scriptInfo.ts b/src/server/scriptInfo.ts
index 6d439e92385..133879a2dce 100644
--- a/src/server/scriptInfo.ts
+++ b/src/server/scriptInfo.ts
@@ -328,6 +328,10 @@ namespace ts.server {
             }
         }
 
+        isOrphan() {
+            return this.containingProjects.length === 0;
+        }
+
         /**
          *  @param line 1 based index
          */