diff --git a/lib/system/gc.nim b/lib/system/gc.nim
index 9e0215b65c..6a8490d639 100644
--- a/lib/system/gc.nim
+++ b/lib/system/gc.nim
@@ -663,16 +663,16 @@ proc collectCycles(gch: var GcHeap) =
 proc gcMark(gch: var GcHeap, p: pointer) {.inline.} =
   # the addresses are not as cells on the stack, so turn them to cells:
   sysAssert(allocInv(gch.region), "gcMark begin")
-  var cell = usrToCell(p)
-  var c = cast[ByteAddress](cell)
+  var c = cast[ByteAddress](p)
   if c >% PageSize:
     # fast check: does it look like a cell?
-    var objStart = cast[PCell](interiorAllocatedPtr(gch.region, cell))
+    var objStart = cast[PCell](interiorAllocatedPtr(gch.region, p))
     if objStart != nil:
       # mark the cell:
       incRef(objStart)
       add(gch.decStack, objStart)
     when false:
+      let cell = usrToCell(p)
       if isAllocatedPtr(gch.region, cell):
         sysAssert false, "allocated pointer but not interior?"
         # mark the cell:
diff --git a/lib/system/gc_ms.nim b/lib/system/gc_ms.nim
index 852f5d7aa4..ae73404158 100644
--- a/lib/system/gc_ms.nim
+++ b/lib/system/gc_ms.nim
@@ -455,11 +455,10 @@ proc markGlobals(gch: var GcHeap) =
 
 proc gcMark(gch: var GcHeap, p: pointer) {.inline.} =
   # the addresses are not as cells on the stack, so turn them to cells:
-  var cell = usrToCell(p)
-  var c = cast[ByteAddress](cell)
+  var c = cast[ByteAddress](p)
   if c >% PageSize:
     # fast check: does it look like a cell?
-    var objStart = cast[PCell](interiorAllocatedPtr(gch.region, cell))
+    var objStart = cast[PCell](interiorAllocatedPtr(gch.region, p))
     if objStart != nil:
       mark(gch, objStart)