diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index ec220ad248e..7932c6874d9 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -268,7 +268,7 @@ namespace ts {
         return s;
     }
 
-    export function formatDiagnosticsWithColorAndContext(diagnostics: Diagnostic[], host: FormatDiagnosticsHost): string {
+    export function formatDiagnosticsWithColorAndContext(diagnostics: ReadonlyArray<Diagnostic>, host: FormatDiagnosticsHost): string {
         let output = "";
         for (const diagnostic of diagnostics) {
             if (diagnostic.file) {
@@ -284,12 +284,12 @@ namespace ts {
                     gutterWidth = Math.max(ellipsis.length, gutterWidth);
                 }
 
-                output += sys.newLine;
+                output += host.getNewLine();
                 for (let i = firstLine; i <= lastLine; i++) {
                     // If the error spans over 5 lines, we'll only show the first 2 and last 2 lines,
                     // so we'll skip ahead to the second-to-last line.
                     if (hasMoreThanFiveLines && firstLine + 1 < i && i < lastLine - 1) {
-                        output += formatAndReset(padLeft(ellipsis, gutterWidth), gutterStyleSequence) + gutterSeparator + sys.newLine;
+                        output += formatAndReset(padLeft(ellipsis, gutterWidth), gutterStyleSequence) + gutterSeparator + host.getNewLine();
                         i = lastLine - 1;
                     }
 
@@ -301,7 +301,7 @@ namespace ts {
 
                     // Output the gutter and the actual contents of the line.
                     output += formatAndReset(padLeft(i + 1 + "", gutterWidth), gutterStyleSequence) + gutterSeparator;
-                    output += lineContent + sys.newLine;
+                    output += lineContent + host.getNewLine();
 
                     // Output the gutter and the error span for the line using tildes.
                     output += formatAndReset(padLeft("", gutterWidth), gutterStyleSequence) + gutterSeparator;
@@ -323,17 +323,17 @@ namespace ts {
                     }
                     output += resetEscapeSequence;
 
-                    output += sys.newLine;
+                    output += host.getNewLine();
                 }
 
-                output += sys.newLine;
+                output += host.getNewLine();
                 output += `${ relativeFileName }(${ firstLine + 1 },${ firstLineChar + 1 }): `;
             }
 
             const categoryColor = getCategoryFormat(diagnostic.category);
             const category = DiagnosticCategory[diagnostic.category].toLowerCase();
-            output += `${ formatAndReset(category, categoryColor) } TS${ diagnostic.code }: ${ flattenDiagnosticMessageText(diagnostic.messageText, sys.newLine) }`;
-            output += sys.newLine;
+            output += `${ formatAndReset(category, categoryColor) } TS${ diagnostic.code }: ${ flattenDiagnosticMessageText(diagnostic.messageText, host.getNewLine()) }`;
+            output += host.getNewLine();
         }
         return output;
     }
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index a130d8427da..c9c14198279 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -337,7 +337,7 @@ namespace ts {
             Debug.assert(res < lineStarts[line + 1]);
         }
         else if (debugText !== undefined) {
-            Debug.assert(res < debugText.length);
+            Debug.assert(res <= debugText.length); // Allow single character overflow for trailing newline
         }
         return res;
     }
diff --git a/src/harness/compilerRunner.ts b/src/harness/compilerRunner.ts
index 170a23e34f2..a600c7dd857 100644
--- a/src/harness/compilerRunner.ts
+++ b/src/harness/compilerRunner.ts
@@ -141,7 +141,7 @@ class CompilerBaselineRunner extends RunnerBase {
 
             // check errors
             it("Correct errors for " + fileName, () => {
-                Harness.Compiler.doErrorBaseline(justName, tsConfigFiles.concat(toBeCompiled, otherFiles), result.errors);
+                Harness.Compiler.doErrorBaseline(justName, tsConfigFiles.concat(toBeCompiled, otherFiles), result.errors, !!options.pretty);
             });
 
             it (`Correct module resolution tracing for ${fileName}`, () => {
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 9443844cf9a..2fc1aac2d83 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -1284,11 +1284,12 @@ namespace Harness {
             return normalized;
         }
 
-        export function minimalDiagnosticsToString(diagnostics: ReadonlyArray<ts.Diagnostic>) {
-            return ts.formatDiagnostics(diagnostics, { getCanonicalFileName, getCurrentDirectory: () => "", getNewLine: () => Harness.IO.newLine() });
+        export function minimalDiagnosticsToString(diagnostics: ReadonlyArray<ts.Diagnostic>, pretty?: boolean) {
+            const host = { getCanonicalFileName, getCurrentDirectory: () => "", getNewLine: () => Harness.IO.newLine() };
+            return (pretty ? ts.formatDiagnosticsWithColorAndContext : ts.formatDiagnostics)(diagnostics, host);
         }
 
-        export function getErrorBaseline(inputFiles: ReadonlyArray<TestFile>, diagnostics: ReadonlyArray<ts.Diagnostic>) {
+        export function getErrorBaseline(inputFiles: ReadonlyArray<TestFile>, diagnostics: ReadonlyArray<ts.Diagnostic>, pretty?: boolean) {
             diagnostics = diagnostics.slice().sort(ts.compareDiagnostics);
             let outputLines = "";
             // Count up all errors that were found in files other than lib.d.ts so we don't miss any
@@ -1408,18 +1409,18 @@ namespace Harness {
             // Verify we didn't miss any errors in total
             assert.equal(totalErrorsReportedInNonLibraryFiles + numLibraryDiagnostics + numTest262HarnessDiagnostics, diagnostics.length, "total number of errors");
 
-            return minimalDiagnosticsToString(diagnostics) +
+            return minimalDiagnosticsToString(diagnostics, pretty) +
                 Harness.IO.newLine() + Harness.IO.newLine() + outputLines;
         }
 
-        export function doErrorBaseline(baselinePath: string, inputFiles: TestFile[], errors: ts.Diagnostic[]) {
+        export function doErrorBaseline(baselinePath: string, inputFiles: TestFile[], errors: ts.Diagnostic[], pretty?: boolean) {
             Harness.Baseline.runBaseline(baselinePath.replace(/\.tsx?$/, ".errors.txt"), (): string => {
                 if (!errors || (errors.length === 0)) {
                     /* tslint:disable:no-null-keyword */
                     return null;
                     /* tslint:enable:no-null-keyword */
                 }
-                return getErrorBaseline(inputFiles, errors);
+                return getErrorBaseline(inputFiles, errors, pretty);
             });
         }
 
diff --git a/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt b/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt
new file mode 100644
index 00000000000..7b7e3fea3e3
--- /dev/null
+++ b/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt
@@ -0,0 +1,12 @@
+
+2 
+  
+
+tests/cases/compiler/index.ts(2,1): error TS1005: '}' expected.
+
+
+==== tests/cases/compiler/index.ts (1 errors) ====
+    if (true) {
+    
+    
+!!! error TS1005: '}' expected.
\ No newline at end of file
diff --git a/tests/baselines/reference/prettyContextNotDebugAssertion.js b/tests/baselines/reference/prettyContextNotDebugAssertion.js
new file mode 100644
index 00000000000..1051f76864c
--- /dev/null
+++ b/tests/baselines/reference/prettyContextNotDebugAssertion.js
@@ -0,0 +1,7 @@
+//// [index.ts]
+if (true) {
+
+
+//// [index.js]
+if (true) {
+}
diff --git a/tests/cases/compiler/prettyContextNotDebugAssertion.ts b/tests/cases/compiler/prettyContextNotDebugAssertion.ts
new file mode 100644
index 00000000000..d65b02d472f
--- /dev/null
+++ b/tests/cases/compiler/prettyContextNotDebugAssertion.ts
@@ -0,0 +1,3 @@
+// @pretty: true
+// @filename: index.ts
+if (true) {