diff --git a/internal/engine/compiler/engine.go b/internal/engine/compiler/engine.go
index 078d46f7..ac9b7fea 100644
--- a/internal/engine/compiler/engine.go
+++ b/internal/engine/compiler/engine.go
@@ -348,13 +348,13 @@ const (
 	functionSize                     = 56
 
 	// Offsets for wasm.ModuleInstance.
-	moduleInstanceGlobalsOffset          = 24
-	moduleInstanceMemoryOffset           = 48
-	moduleInstanceTablesOffset           = 56
-	moduleInstanceEngineOffset           = 80
-	moduleInstanceTypeIDsOffset          = 96
-	moduleInstanceDataInstancesOffset    = 120
-	moduleInstanceElementInstancesOffset = 144
+	moduleInstanceGlobalsOffset          = 32
+	moduleInstanceMemoryOffset           = 56
+	moduleInstanceTablesOffset           = 64
+	moduleInstanceEngineOffset           = 88
+	moduleInstanceTypeIDsOffset          = 104
+	moduleInstanceDataInstancesOffset    = 128
+	moduleInstanceElementInstancesOffset = 152
 
 	// Offsets for wasm.TableInstance.
 	tableInstanceTableOffset    = 0
diff --git a/internal/wasm/store.go b/internal/wasm/store.go
index d768c7e3..0b1cfb00 100644
--- a/internal/wasm/store.go
+++ b/internal/wasm/store.go
@@ -58,6 +58,17 @@ type (
 	//
 	// This implements api.Module.
 	ModuleInstance struct {
+		// Closed is used both to guard moduleEngine.CloseWithExitCode and to store the exit code.
+		//
+		// The update value is closedType + exitCode << 32. This ensures an exit code of zero isn't mistaken for never closed.
+		//
+		// Note: Exclusively reading and updating this with atomics guarantees cross-goroutine observations.
+		// See /RATIONALE.md
+		//
+		// TODO: Retype this to atomic.Unit64 when Go 1.18 is no longer supported. Until then, keep Closed at the top of
+		// this struct. See PR #1299 for an implementation and discussion.
+		Closed uint64
+
 		ModuleName     string
 		Exports        map[string]*Export
 		Globals        []*GlobalInstance
@@ -94,14 +105,6 @@ type (
 		//	  security implications.
 		Sys *internalsys.Context
 
-		// closed is the pointer used both to guard moduleEngine.CloseWithExitCode and to store the exit code.
-		//
-		// The update value is closedType + exitCode << 32. This ensures an exit code of zero isn't mistaken for never closed.
-		//
-		// Note: Exclusively reading and updating this with atomics guarantees cross-goroutine observations.
-		// See /RATIONALE.md
-		Closed uint64
-
 		// CodeCloser is non-nil when the code should be closed after this module.
 		CodeCloser api.Closer