diff --git a/changes/bug5858 b/changes/bug5858
new file mode 100644
index 0000000000..aa1e8bba1d
--- /dev/null
+++ b/changes/bug5858
@@ -0,0 +1,4 @@
+  o Minor bugfixes:
+    - Remove bogus definition of "_WIN32" from src/win32/orconfig.h, to
+      unbreak the MSVC build. Fies bug 5858; bugfix on 0.2.3.12-alpha.
+
diff --git a/src/win32/orconfig.h b/src/win32/orconfig.h
index f6bbf8bc4e..a08d0c6b58 100644
--- a/src/win32/orconfig.h
+++ b/src/win32/orconfig.h
@@ -3,7 +3,6 @@
  */
 
 /* Windows-only defines. */
-#define _WIN32
 #define CONFDIR ""
 
 /* Define to 1 if you have the <arpa/inet.h> header file. */