diff --git a/types/debug/debug-tests.ts b/types/debug/debug-tests.ts
index ddfd698825..22ac083a14 100644
--- a/types/debug/debug-tests.ts
+++ b/types/debug/debug-tests.ts
@@ -3,7 +3,7 @@ import debug = require("debug");
 debug.disable();
 debug.enable("DefinitelyTyped:*");
 
-const log: debug.IDebugger = debug("DefinitelyTyped:log");
+const log: debug.Debugger = debug("DefinitelyTyped:log");
 
 log("Just text");
 log("Formatted test (%d arg)", 1);
@@ -13,12 +13,12 @@ log("Enabled?: %s", debug.enabled("DefinitelyTyped:log"));
 log("Name Enabled: %s", debug.names.some(name => name.test("DefinitelyTyped:log")));
 log("Namespace: %s", log.namespace);
 
-const error: debug.IDebugger = debug("DefinitelyTyped:error");
+const error: debug.Debugger = debug("DefinitelyTyped:error");
 error.log = console.error.bind(console);
 error("This should be printed to stderr");
 
-const extendedLog: debug.IDebugger = log.extend('extended');
+const extendedLog: debug.Debugger = log.extend('extended');
 extendedLog("Testing this is also an IDebugger.");
 
-const extendedWithCustomDelimiter: debug.IDebugger = log.extend('with-delim', '.');
+const extendedWithCustomDelimiter: debug.Debugger = log.extend('with-delim', '.');
 extendedWithCustomDelimiter("Testing this is an IDebugger, too.");