diff --git a/lib/system.nim b/lib/system.nim
index 221a538b13..3ba2050b63 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -2055,7 +2055,11 @@ export dollars
 
 const
   NimMajor* {.intdefine.}: int = 1
-    ## is the major number of Nim's version.
+    ## is the major number of Nim's version. Example:
+    ##
+    ## .. code-block:: Nim
+    ##   when (NimMajor, NimMinor, NimPatch) >=  (1, 3, 1): discard
+    # See also private symbol `since: (1, 3)` reserved for stdlib
 
   NimMinor* {.intdefine.}: int = 3
     ## is the minor number of Nim's version.
diff --git a/lib/system/inclrtl.nim b/lib/system/inclrtl.nim
index e84794c745..37cdb74d8f 100644
--- a/lib/system/inclrtl.nim
+++ b/lib/system/inclrtl.nim
@@ -49,8 +49,20 @@ when defined(nimlocks):
 else:
   {.pragma: benign, gcsafe.}
 
+template isSince(version: (int, int)): bool =
+  (NimMajor, NimMinor) >= version
+template isSince(version: (int, int, int)): bool =
+  (NimMajor, NimMinor, NimPatch) >= version
+
 template since(version, body: untyped) {.dirty, used.} =
-  ## limitation: can't be used to annotate a template (eg typetraits.get), would
+  ## Usage:
+  ##
+  ## .. code-block:: Nim
+  ##   proc fun*() {since: (1, 3).}
+  ##   proc fun*() {since: (1, 3, 1).}
+  ##
+  ## Limitation: can't be used to annotate a template (eg typetraits.get), would
   ## error: cannot attach a custom pragma.
-  when (NimMajor, NimMinor) >= version:
+  # `dirty` needed because `NimMajor` may not yet be defined in caller.
+  when isSince(version):
     body
diff --git a/tests/stdlib/tinclrtl.nim b/tests/stdlib/tinclrtl.nim
new file mode 100644
index 0000000000..2d4c34a909
--- /dev/null
+++ b/tests/stdlib/tinclrtl.nim
@@ -0,0 +1,32 @@
+include system/inclrtl
+
+proc fun1(): int {.since: (1,3).} = 12
+proc fun1Bad(): int {.since: (99,3).} = 12
+proc fun2(): int {.since: (1,3,1).} = 12
+proc fun2Bad(): int {.since: (99,3,1).} = 12
+
+doAssert fun1() == 12
+doAssert declared(fun1)
+doAssert not declared(fun1Bad)
+
+doAssert fun2() == 12
+doAssert declared(fun2)
+doAssert not declared(fun2Bad)
+
+var ok = false
+since (1, 3):
+  ok = true
+doAssert ok
+
+ok = false
+since (1, 3, 1):
+  ok = true
+doAssert ok
+
+since (99,3):
+  doAssert false
+
+when false:
+  # pending https://github.com/timotheecour/Nim/issues/129
+  # Error: cannot attach a custom pragma to 'fun3'
+  template fun3(): int {.since: (1, 3).} = 12