diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 171d656230..df50d93954 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -2940,6 +2940,13 @@ proc genEnumToStr(p: BProc, e: PNode, d: var TLoc) =
 
 proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
   case op
+  of mAsgn:
+    let kind = if e[0].sym.name.s == "=sink": nkSinkAsgn else: nkAsgn
+    let lhs = e[1].skipHiddenAddr
+    let n = newTreeI(kind, e.info, lhs, e[2])
+    n.typ = e.typ
+    cow(p, e[2])
+    genAsgn(p, n, fastAsgn = kind != nkAsgn)
   of mOr, mAnd: genAndOr(p, e, d, op)
   of mNot..mUnaryMinusF64: unaryArith(p, e, d, op)
   of mUnaryMinusI..mAbsI: unaryArithOverflow(p, e, d, op)
diff --git a/tests/arc/tisolated_primitive.nim b/tests/arc/tisolated_primitive.nim
new file mode 100644
index 0000000000..05e760b155
--- /dev/null
+++ b/tests/arc/tisolated_primitive.nim
@@ -0,0 +1,12 @@
+# Issue: genMagicExpr: mAsgn internal error when using Isolated[T] with primitive types
+# in tuple assignment to pointer dereference
+
+import std/isolation
+
+proc main() =
+  var x: ptr Isolated[float]
+  x = cast[ptr Isolated[float]](alloc0(sizeof(Isolated[float])))
+  x[] = isolate(42.0)
+  dealloc(x)
+
+main()