diff --git a/lib/vtls/schannel.c b/lib/vtls/schannel.c
index 34d48126b4..6226f427bf 100644
--- a/lib/vtls/schannel.c
+++ b/lib/vtls/schannel.c
@@ -81,26 +81,26 @@
 #endif
 #endif
 
+/* Offered by mingw-w64 v8+. MS SDK 7.0A+. */
 #ifndef SP_PROT_TLS1_0_CLIENT
 #define SP_PROT_TLS1_0_CLIENT           SP_PROT_TLS1_CLIENT
 #endif
-
 #ifndef SP_PROT_TLS1_1_CLIENT
 #define SP_PROT_TLS1_1_CLIENT           0x00000200
 #endif
-
 #ifndef SP_PROT_TLS1_2_CLIENT
 #define SP_PROT_TLS1_2_CLIENT           0x00000800
 #endif
 
+/* Offered by mingw-w64 v8+. MS SDK ~10+/~VS2017+. */
 #ifndef SP_PROT_TLS1_3_CLIENT
 #define SP_PROT_TLS1_3_CLIENT           0x00002000
 #endif
-
 #ifndef SCH_USE_STRONG_CRYPTO
 #define SCH_USE_STRONG_CRYPTO           0x00400000
 #endif
 
+/* Offered by mingw-w64 v10+. MS SDK 7.0A+. */
 #ifndef SECBUFFER_ALERT
 #define SECBUFFER_ALERT                 17
 #endif