diff --git a/changes/bug5858 b/changes/bug5858
new file mode 100644
index 0000000000000000000000000000000000000000..aa1e8bba1da967bd8c02acc83e32dad32c1584c0
--- /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 f6bbf8bc4e8255efad426d1703b7c8fbd2e5bd2e..a08d0c6b5867fe38aeda30406e86a3f0cd174f4d 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. */