diff --git a/UserManual.md b/UserManual.md
index 701ee2457c91f65dd828dbb676336c9c53810d99..5f6904e5997fa1d2ba448609306f2192be9c846b 100644
--- a/UserManual.md
+++ b/UserManual.md
@@ -357,6 +357,10 @@ variable is visible in the block that follows.
   the Manual should be of help. Note: the syntax changes from time to time,
   so updating the config file might be necessary after executable update.
 
+- Embedding with OpenSSL on Windows might fail because of calling convention.
+  To force Mongoose to use `__stdcall` convention, add `/Gz` compilation
+  flag in Visual Studio compiler.
+
 # Embedding
 Embedding Mongoose is easy. Copy
 [mongoose.c](https://github.com/valenok/mongoose/blob/master/mongoose.c) and