diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
index 1328a2e84844c..0c7fa5e8dda87 100644
--- a/src/compiler/declarationEmitter.ts
+++ b/src/compiler/declarationEmitter.ts
@@ -33,7 +33,7 @@ namespace ts {
     export function getDeclarationDiagnostics(host: EmitHost, resolver: EmitResolver, targetSourceFile: SourceFile): Diagnostic[] {
         const declarationDiagnostics = createDiagnosticCollection();
         forEachExpectedEmitFile(host, getDeclarationDiagnosticsFromFile, targetSourceFile);
-        return declarationDiagnostics.getDiagnostics(targetSourceFile.fileName);
+        return declarationDiagnostics.getDiagnostics(targetSourceFile ? targetSourceFile.fileName : undefined);
 
         function getDeclarationDiagnosticsFromFile({ declarationFilePath }, sources: SourceFile[], isBundledEmit: boolean) {
             emitDeclarations(host, resolver, declarationDiagnostics, declarationFilePath, sources, isBundledEmit);
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 2f832e72c51fb..b051c0f5bccbf 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -1030,7 +1030,14 @@ namespace ts {
         }
 
         function getDeclarationDiagnostics(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
-            return getDiagnosticsHelper(sourceFile, getDeclarationDiagnosticsForFile, cancellationToken);
+            const options = program.getCompilerOptions();
+            // collect diagnostics from the program only once if either no source file was specified or out/outFile is set (bundled emit)
+            if (!sourceFile || options.out || options.outFile) {
+                return getDeclarationDiagnosticsWorker(sourceFile, cancellationToken);
+            }
+            else {
+                return getDiagnosticsHelper(sourceFile, getDeclarationDiagnosticsForFile, cancellationToken);
+            }
         }
 
         function getSyntacticDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
@@ -1244,17 +1251,19 @@ namespace ts {
             });
         }
 
-        function getDeclarationDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
+        function getDeclarationDiagnosticsWorker(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
             return runWithCancellationToken(() => {
-                if (!isDeclarationFile(sourceFile)) {
-                    const resolver = getDiagnosticsProducingTypeChecker().getEmitResolver(sourceFile, cancellationToken);
-                    // Don't actually write any files since we're just getting diagnostics.
-                    const writeFile: WriteFileCallback = () => { };
-                    return ts.getDeclarationDiagnostics(getEmitHost(writeFile), resolver, sourceFile);
-                }
+                const resolver = getDiagnosticsProducingTypeChecker().getEmitResolver(sourceFile, cancellationToken);
+                // Don't actually write any files since we're just getting diagnostics.
+                const writeFile: WriteFileCallback = () => { };
+                return ts.getDeclarationDiagnostics(getEmitHost(writeFile), resolver, sourceFile);
             });
         }
 
+        function getDeclarationDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
+            return isDeclarationFile(sourceFile) ? [] : getDeclarationDiagnosticsWorker(sourceFile, cancellationToken);
+        }
+
         function getOptionsDiagnostics(): Diagnostic[] {
             const allDiagnostics: Diagnostic[] = [];
             addRange(allDiagnostics, fileProcessingDiagnostics.getGlobalDiagnostics());