diff --git a/tests/cases/fourslash/formattingReplaceSpacesWithTabs.ts b/tests/cases/fourslash/formattingReplaceSpacesWithTabs.ts
new file mode 100644
index 00000000000..37039c5a7ad
--- /dev/null
+++ b/tests/cases/fourslash/formattingReplaceSpacesWithTabs.ts
@@ -0,0 +1,35 @@
+/// <reference path="fourslash.ts"/>
+
+////module Foo {
+/////*1*/class Test { }
+/////*2*/ class Test { }
+/////*3*/    class Test { }
+/////*4*/     class Test { }
+/////*5*/	class Test { }
+/////*6*/	 class Test { }
+/////*7*/		class Test { }
+////}
+
+var options = format.copyFormatOptions();
+options.ConvertTabsToSpaces = false;
+var oldOptions = format.setFormatOptions(options);
+try {
+    format.document();
+    goTo.marker("1");
+    verify.currentLineContentIs("\tclass Test { }")
+    goTo.marker("2");
+    verify.currentLineContentIs("\tclass Test { }")
+    goTo.marker("3");
+    verify.currentLineContentIs("\tclass Test { }")
+    goTo.marker("4");
+    verify.currentLineContentIs("\tclass Test { }")
+    goTo.marker("5");
+    verify.currentLineContentIs("\tclass Test { }")
+    goTo.marker("6");
+    verify.currentLineContentIs("\tclass Test { }")
+    goTo.marker("7");
+    verify.currentLineContentIs("\tclass Test { }")
+}
+finally {
+    format.setFormatOptions(oldOptions);
+}
diff --git a/tests/cases/fourslash/formattingReplaceTabsWithSpaces.ts b/tests/cases/fourslash/formattingReplaceTabsWithSpaces.ts
new file mode 100644
index 00000000000..ad5b5508c4f
--- /dev/null
+++ b/tests/cases/fourslash/formattingReplaceTabsWithSpaces.ts
@@ -0,0 +1,27 @@
+/// <reference path="fourslash.ts"/>
+
+////module Foo {
+/////*1*/				class Test { }
+/////*2*/			class Test { }
+/////*3*/class Test { }
+/////*4*/			 class Test { }
+/////*5*/   class Test { }
+/////*6*/    class Test { }
+/////*7*/     class Test { }
+////}
+
+format.document();
+goTo.marker("1");
+verify.currentLineContentIs("    class Test { }")
+goTo.marker("2");
+verify.currentLineContentIs("    class Test { }")
+goTo.marker("3");
+verify.currentLineContentIs("    class Test { }")
+goTo.marker("4");
+verify.currentLineContentIs("    class Test { }")
+goTo.marker("5");
+verify.currentLineContentIs("    class Test { }")
+goTo.marker("6");
+verify.currentLineContentIs("    class Test { }")
+goTo.marker("7");
+verify.currentLineContentIs("    class Test { }")