diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 083c812464d..b94efe18222 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -887,18 +887,28 @@ namespace ts {
             return sourceFile.parseDiagnostics;
         }
 
-        function onCancel() {
-            // Because our type checker might be a bad state, we need to throw it away.
-            // Note: we are overly aggressive here.  We do not actually *have* to throw away
-            // the "noDiagnosticsTypeChecker".  However, for simplicity, i'd like to keep
-            // the lifetimes of these two TypeCheckers the same.  Also, we generally only
-            // cancel when the user has made a change anyways.  And, in that case, we (the
-            // program instance) will get thrown away anyways.  So trying to keep one of
-            // these type checkers alive doesn't serve much purpose.
-            noDiagnosticsTypeChecker = undefined;
-            diagnosticsProducingTypeChecker = undefined;
-        }
+        function runWithCancellationToken<T>(func: () => T): T {
+            try {
+                return func();
+            }
+            catch (e) {
+                if (e instanceof OperationCanceledException) {
+                    // We were canceled while performing the operation.  Because our type checker
+                    // might be a bad state, we need to throw it away.
+                    //
+                    // Note: we are overly aggressive here.  We do not actually *have* to throw away
+                    // the "noDiagnosticsTypeChecker".  However, for simplicity, i'd like to keep
+                    // the lifetimes of these two TypeCheckers the same.  Also, we generally only
+                    // cancel when the user has made a change anyways.  And, in that case, we (the
+                    // program instance) will get thrown away anyways.  So trying to keep one of
+                    // these type checkers alive doesn't serve much purpose.
+                    noDiagnosticsTypeChecker = undefined;
+                    diagnosticsProducingTypeChecker = undefined;
+                }
 
+                throw e;
+            }
+        }
 
         function getSemanticDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
             return runWithCancellationToken(() => {
@@ -914,7 +924,7 @@ namespace ts {
                 const programDiagnosticsInFile = programDiagnostics.getDiagnostics(sourceFile.fileName);
 
                 return bindDiagnostics.concat(checkDiagnostics, fileProcessingDiagnosticsInFile, programDiagnosticsInFile);
-            }, onCancel);
+            });
         }
 
         function getJavaScriptSyntacticDiagnosticsForFile(sourceFile: SourceFile): Diagnostic[] {
@@ -1093,7 +1103,7 @@ namespace ts {
                 function createDiagnosticForNode(node: Node, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number): Diagnostic {
                     return createDiagnosticForNodeInSourceFile(sourceFile, node, message, arg0, arg1, arg2);
                 }
-            }, onCancel);
+            });
         }
 
         function getDeclarationDiagnosticsWorker(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
@@ -1101,7 +1111,7 @@ namespace ts {
                 const resolver = getDiagnosticsProducingTypeChecker().getEmitResolver(sourceFile, cancellationToken);
                 // Don't actually write any files since we're just getting diagnostics.
                 return ts.getDeclarationDiagnostics(getEmitHost(noop), resolver, sourceFile);
-            }, onCancel);
+            });
         }
 
         function getDeclarationDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index 2910a3528d0..62ead677d8b 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -17,21 +17,27 @@ namespace ts.NavigationBar {
     export function getNavigationBarItems(sourceFile: SourceFile, cancellationToken: ThrottledCancellationToken): NavigationBarItem[] {
         curCancellationToken = cancellationToken;
         curSourceFile = sourceFile;
-        const result = runWithCancellationToken(() => map(topLevelItems(rootNavigationBarNode(sourceFile)), convertToTopLevelItem), () => curSourceFile = undefined);
-        curSourceFile = undefined;
-        return result;
+        try {
+            return map(topLevelItems(rootNavigationBarNode(sourceFile)), convertToTopLevelItem);
+        }
+        finally {
+            curSourceFile = undefined;
+        }
     }
 
     export function getNavigationTree(sourceFile: SourceFile, cancellationToken: ThrottledCancellationToken): NavigationTree {
         curCancellationToken = cancellationToken;
         curSourceFile = sourceFile;
-        const result = runWithCancellationToken(() => convertToTree(rootNavigationBarNode(sourceFile)), () => curSourceFile = undefined);
-        curSourceFile = undefined;
-        return result;
+        try {
+            return convertToTree(rootNavigationBarNode(sourceFile));
+        }
+        finally {
+            curSourceFile = undefined;
+        }
     }
 
     // Keep sourceFile handy so we don't have to search for it every time we need to call `getText`.
-    let curCancellationToken: ThrottledCancellationToken;
+    let curCancellationToken: CancellationToken;
     let curSourceFile: SourceFile;
     function nodeText(node: Node): string {
         return node.getText(curSourceFile);
@@ -63,7 +69,7 @@ namespace ts.NavigationBar {
         const root: NavigationBarNode = { node: sourceFile, additionalNodes: undefined, parent: undefined, children: undefined, indent: 0 };
         parent = root;
         for (const statement of sourceFile.statements) {
-            addChildrenRecursively(statement, curCancellationToken);
+            addChildrenRecursively(statement);
         }
         endNode();
         Debug.assert(!parent && !parentsStack.length);
@@ -113,9 +119,9 @@ namespace ts.NavigationBar {
     }
 
     /** Look for navigation bar items in node's subtree, adding them to the current `parent`. */
-    function addChildrenRecursively(node: Node, cancellationToken: ThrottledCancellationToken): void {
+    function addChildrenRecursively(node: Node): void {
         function addChildrenRecursively(node: Node): void {
-            cancellationToken.throwIfCancellationRequested();
+            curCancellationToken.throwIfCancellationRequested();
 
             if (!node || isToken(node)) {
                 return;