diff --git a/Modules/_lzmamodule.c b/Modules/_lzmamodule.c
--- a/Modules/_lzmamodule.c
+++ b/Modules/_lzmamodule.c
@@ -280,6 +280,9 @@
     return options;
 }
 
+#ifdef _MSC_VER
+  #pragma optimize("", off)
+#endif
 static void *
 parse_filter_spec(lzma_filter *f, PyObject *spec)
 {
@@ -323,6 +326,9 @@
             return NULL;
     }
 }
+#ifdef _MSC_VER
+  #pragma optimize("", on)
+#endif
 
 static void
 free_filter_chain(lzma_filter filters[])
@@ -385,6 +391,9 @@
     return status;
 }
 
+#ifdef _MSC_VER
+  #pragma optimize("", off)
+#endif
 static PyObject *
 build_filter_spec(const lzma_filter *f)
 {
@@ -448,6 +457,9 @@
     Py_DECREF(spec);
     return NULL;
 }
+#ifdef _MSC_VER
+  #pragma optimize("", on)
+#endif
 
 
 /* LZMACompressor class. */
diff --git a/Objects/memoryobject.c b/Objects/memoryobject.c
--- a/Objects/memoryobject.c
+++ b/Objects/memoryobject.c
@@ -1541,6 +1541,9 @@
 }
 
 #ifdef HAVE_LONG_LONG
+#ifdef _MSC_VER
+  #pragma optimize("", off)
+#endif
 static PY_LONG_LONG
 pylong_as_lld(PyObject *item)
 {
@@ -1570,6 +1573,9 @@
     Py_DECREF(tmp);
     return llu;
 }
+#ifdef _MSC_VER
+  #pragma optimize("", on)
+#endif
 #endif
 
 static Py_ssize_t