diff --git a/src/Init/Meta/Defs.lean b/src/Init/Meta/Defs.lean
index 3676599c6dba..1d5c74c59848 100644
--- a/src/Init/Meta/Defs.lean
+++ b/src/Init/Meta/Defs.lean
@@ -71,14 +71,14 @@ def toolchain :=
       String.Internal.append
         (String.Internal.append
           (String.Internal.append
-            (String.Internal.append origin ":")
+            (String.Internal.append origin ":v")
             versionStringCore)
           "-")
         version.specialDesc
     else
       String.Internal.append (String.Internal.append origin ":") version.specialDesc
   else if version.isRelease then
-    String.Internal.append (String.Internal.append origin ":") versionStringCore
+    String.Internal.append (String.Internal.append origin ":v") versionStringCore
   else
     ""