diff --git a/qmake/generators/win32/msvc_nmake.cpp b/qmake/generators/win32/msvc_nmake.cpp
index 8b40d4e935..01243defd3 100644
--- a/qmake/generators/win32/msvc_nmake.cpp
+++ b/qmake/generators/win32/msvc_nmake.cpp
@@ -304,6 +304,11 @@ void NmakeMakefileGenerator::init()
         project->values("QMAKE_CLEAN").append(project->first("DESTDIR") + project->first("TARGET") + version + ".ilk");
         project->values("QMAKE_CLEAN").append("vc*.pdb");
         project->values("QMAKE_CLEAN").append("vc*.idb");
+        project->values("DEFINES").removeAll("NDEBUG");
+    } else {
+        ProStringList &defines = project->values("DEFINES");
+        if (!defines.contains("NDEBUG"))
+            defines.append("NDEBUG");
     }
 }