diff --git a/LEGO1/decomp.h b/LEGO1/decomp.h
index 512af280..5466e6d8 100644
--- a/LEGO1/decomp.h
+++ b/LEGO1/decomp.h
@@ -2,6 +2,7 @@
 #define DECOMP_H
 
 #define DECOMP_STATIC_ASSERT(V) namespace { typedef int foo[(V)?1:-1]; }
+#define DECOMP_SIZE_ASSERT(T, S) DECOMP_STATIC_ASSERT(sizeof(T) == S)
 
 typedef unsigned char undefined;
 typedef unsigned short undefined2;
diff --git a/LEGO1/legoinputmanager.cpp b/LEGO1/legoinputmanager.cpp
index 1b97e917..6c0bd709 100644
--- a/LEGO1/legoinputmanager.cpp
+++ b/LEGO1/legoinputmanager.cpp
@@ -2,7 +2,7 @@
 
 #include "decomp.h"
 
-DECOMP_STATIC_ASSERT(sizeof(LegoInputManager) == 824); // 0x10059085
+DECOMP_SIZE_ASSERT(LegoInputManager, 0x338); // 0x10059085
 
 // OFFSET: LEGO1 0x1005b790 STUB
 LegoInputManager::LegoInputManager()