diff --git a/compiler/ast.nim b/compiler/ast.nim
index 5ff986776c3e..2f6c272320ea 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -1645,7 +1645,7 @@ proc propagateToOwner*(owner, elem: PType; propagateHasAsgn = true) =
   if mask != {} and propagateHasAsgn:
     let o2 = owner.skipTypes({tyGenericInst, tyAlias, tySink})
     if o2.kind in {tyTuple, tyObject, tyArray,
-                   tySequence, tySet, tyDistinct}:
+                   tySequence, tyString, tySet, tyDistinct}:
       o2.flags.incl mask
       owner.flags.incl mask
 
diff --git a/tests/metatype/ttypetraits.nim b/tests/metatype/ttypetraits.nim
index 0523390a760c..74ace75c3acd 100644
--- a/tests/metatype/ttypetraits.nim
+++ b/tests/metatype/ttypetraits.nim
@@ -1,3 +1,7 @@
+discard """
+  joinable: false
+"""
+
 import typetraits
 import macros
 
@@ -402,3 +406,26 @@ when true: # Odd bug where alias can seep inside of `distinctBase`
   proc `$`*[T: AdtChild](adtChild: T): string = ""
 
   check 10 is int
+
+
+block: # bug #24378
+  macro forked(body: typed): untyped = # typed or untyped does not matter
+    result = quote do:
+      type Win = typeof(`body`)
+      doAssert not supportsCopyMem((int, Win))
+      doAssert not supportsCopyMem(tuple[a: int, b: Win])
+
+      type Win2[T] = typeof(`body`)
+      doAssert not supportsCopyMem((int, Win2[int]))
+      doAssert not supportsCopyMem(tuple[a: int, b: Win2[int]])
+  forked:
+    "foobar"
+
+
+  type Win111 = typeof("foobar")
+  doAssert not supportsCopyMem((int, Win111))
+  doAssert not supportsCopyMem(tuple[a: int, b: Win111])
+
+  type Win222[T] = typeof("foobar")
+  doAssert not supportsCopyMem((int, Win222[int]))
+  doAssert not supportsCopyMem(tuple[a: int, b: Win222[int]])