diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index fcedcf001e..d8f5d016b1 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -2156,7 +2156,7 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
     const opr: array[mInc..mDec, string] = ["+=", "-="]
     const fun64: array[mInc..mDec, string] = ["nimAddInt64", "nimSubInt64"]
     const fun: array[mInc..mDec, string] = ["nimAddInt","nimSubInt"]
-    let underlying = skipTypes(e[1].typ, {tyGenericInst, tyAlias, tySink, tyVar, tyLent, tyRange})
+    let underlying = skipTypes(e[1].typ, {tyGenericInst, tyAlias, tySink, tyVar, tyLent, tyRange, tyDistinct})
     if optOverflowCheck notin p.options or underlying.kind in {tyUInt..tyUInt64}:
       binaryStmt(p, e, d, opr[op])
     else:
diff --git a/tests/ccgbugs/t13902.nim b/tests/ccgbugs/t13902.nim
new file mode 100644
index 0000000000..fd4f76d15e
--- /dev/null
+++ b/tests/ccgbugs/t13902.nim
@@ -0,0 +1,12 @@
+
+#issue #13902
+block:
+  type Slot = distinct uint64
+  var s = Slot(1)
+  proc `$`(x: Slot): string {.borrow.}
+  proc `+=`(x: var Slot, y: uint64) {.borrow.}
+  # test was failing with either 0 or 2 echos but not with 1 echo
+  # echo "s = ", s
+  s += 1
+  # echo "s = ", s
+  doAssert s.uint64 == 2, $s # was failing, showing 18419607611339964418