diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 7a19aa9167f..37bc454d614 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -2205,8 +2205,9 @@ namespace ts.projectSystem {
             projectService.checkNumberOfProjects({});
 
             for (const f of [f2, f3]) {
+                // There shouldnt be any script info as we closed the file that resulted in creation of it
                 const scriptInfo = projectService.getScriptInfoForNormalizedPath(server.toNormalizedPath(f.path));
-                assert.equal(scriptInfo.containingProjects.length, 0, `expect 0 containing projects for '${f.path}'`);
+                assert.equal(scriptInfo, undefined, `expected script info to be closed: '${f.path}'`);
             }
         });
 
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 7c0e0a0fb92..ad237bc0337 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -827,10 +827,20 @@ namespace ts.server {
                         this.assignScriptInfoToInferredProjectIfNecessary(f, /*addToListOfOpenFiles*/ false);
                     }
                 }
+
+                // Cleanup script infos that are not open and not part of any project
+                this.deleteOrphanScriptInfoNotInAnyProject();
             }
-            if (info.containingProjects.length === 0) {
-                // if there are not projects that include this script info - delete it
-                this.filenameToScriptInfo.remove(info.path);
+        }
+
+        private deleteOrphanScriptInfoNotInAnyProject() {
+            for (const path of this.filenameToScriptInfo.getKeys()) {
+                const info = this.filenameToScriptInfo.get(path);
+                if (!info.isScriptOpen() && info.containingProjects.length === 0) {
+                    // if there are not projects that include this script info - delete it
+                    info.stopWatcher();
+                    this.filenameToScriptInfo.remove(info.path);
+                }
             }
         }
 
@@ -1418,6 +1428,8 @@ namespace ts.server {
             for (const p of this.inferredProjects) {
                 p.updateGraph();
             }
+
+            this.deleteOrphanScriptInfoNotInAnyProject();
             this.printProjects();
         }
 
diff --git a/src/server/lsHost.ts b/src/server/lsHost.ts
index ec655c545ea..79429737240 100644
--- a/src/server/lsHost.ts
+++ b/src/server/lsHost.ts
@@ -11,11 +11,11 @@ namespace ts.server {
 
         private filesWithChangedSetOfUnresolvedImports: Path[];
 
-        private readonly resolveModuleName: typeof resolveModuleName;
+        private resolveModuleName: typeof resolveModuleName;
         readonly trace: (s: string) => void;
         readonly realpath?: (path: string) => string;
 
-        constructor(private readonly host: ServerHost, private readonly project: Project, private readonly cancellationToken: HostCancellationToken) {
+        constructor(private readonly host: ServerHost, private project: Project, private readonly cancellationToken: HostCancellationToken) {
             this.cancellationToken = new ThrottledCancellationToken(cancellationToken, project.projectService.throttleWaitMilliseconds);
             this.getCanonicalFileName = ts.createGetCanonicalFileName(this.host.useCaseSensitiveFileNames);
 
@@ -47,6 +47,11 @@ namespace ts.server {
             }
         }
 
+        dispose() {
+            this.project = undefined;
+            this.resolveModuleName = undefined;
+        }
+
         public startRecordingFilesWithChangedResolutions() {
             this.filesWithChangedSetOfUnresolvedImports = [];
         }
@@ -238,4 +243,4 @@ namespace ts.server {
             this.compilationSettings = opt;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/server/project.ts b/src/server/project.ts
index be854f948ea..33b345af833 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -116,7 +116,7 @@ namespace ts.server {
 
         public languageServiceEnabled = true;
 
-        protected readonly lsHost: LSHost;
+        protected lsHost: LSHost;
 
         builder: Builder;
         /**
@@ -297,9 +297,15 @@ namespace ts.server {
             this.rootFiles = undefined;
             this.rootFilesMap = undefined;
             this.program = undefined;
+            this.builder = undefined;
+            this.cachedUnresolvedImportsPerFile = undefined;
+            this.projectErrors = undefined;
+            this.lsHost.dispose();
+            this.lsHost = undefined;
 
             // signal language service to release source files acquired from document registry
             this.languageService.dispose();
+            this.languageService = undefined;
         }
 
         getCompilerOptions() {
@@ -1043,6 +1049,7 @@ namespace ts.server {
 
             if (this.projectFileWatcher) {
                 this.projectFileWatcher.close();
+                this.projectFileWatcher = undefined;
             }
 
             if (this.typeRootsWatchers) {
@@ -1132,4 +1139,4 @@ namespace ts.server {
             this.typeAcquisition = newTypeAcquisition;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/services/services.ts b/src/services/services.ts
index 9e17e9a45e1..7adce648a62 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1311,7 +1311,9 @@ namespace ts {
             if (program) {
                 forEach(program.getSourceFiles(), f =>
                     documentRegistry.releaseDocument(f.fileName, program.getCompilerOptions()));
+                program = undefined;
             }
+            host = undefined;
         }
 
         /// Diagnostics