diff --git a/lib/pure/strtabs.nim b/lib/pure/strtabs.nim
index 86f81aa433..0a1cc61676 100644
--- a/lib/pure/strtabs.nim
+++ b/lib/pure/strtabs.nim
@@ -135,15 +135,18 @@ proc enlarge(t: StringTableRef) =
     if not isNil(t.data[i].key): rawInsert(t, n, t.data[i].key, t.data[i].val)
   swap(t.data, n)
 
-proc `[]=`*(t: StringTableRef, key, val: string) {.rtl, extern: "nstPut".} =
-  ## puts a (key, value)-pair into `t`.
+proc addVal(t: StringTableRef, key, val: string) =
   var index = rawGet(t, key)
   if index >= 0:
     t.data[index].val = val
   else:
     if mustRehash(len(t.data), t.counter): enlarge(t)
     rawInsert(t, t.data, key, val)
-    inc(t.counter)
+
+proc `[]=`*(t: StringTableRef, key, val: string) {.rtl, extern: "nstPut".} =
+  ## puts a (key, value)-pair into `t`.
+  t.addVal(key, val)
+  inc(t.counter)
 
 proc raiseFormatException(s: string) =
   var e: ref ValueError