diff --git a/engine/common/hpak.h b/engine/common/hpak.h
index 0b4add17..c6c40265 100644
--- a/engine/common/hpak.h
+++ b/engine/common/hpak.h
@@ -76,6 +76,8 @@ typedef struct
 	int             infotableofs;
 } hpak_header_t;
 
+STATIC_ASSERT( sizeof( hpak_header_t ) == 12, "invalid hpak_header_t size" );
+
 typedef struct
 {
 	dresource_t     resource;
@@ -83,6 +85,8 @@ typedef struct
 	int             disksize;
 } hpak_lump_t;
 
+STATIC_ASSERT( sizeof( hpak_lump_t ) == 144, "invalid hpak_lump_t size" );
+
 typedef struct
 {
 	int             count;
diff --git a/engine/custom.h b/engine/custom.h
index da01f745..04d84894 100644
--- a/engine/custom.h
+++ b/engine/custom.h
@@ -90,4 +90,12 @@ typedef struct customization_s
 #define FCUST_WIPEDATA		( 1<<1 )
 #define FCUST_IGNOREINIT		( 1<<2 )
 
+#if !XASH_64BIT
+STATIC_ASSERT( sizeof( customization_t ) == 164, "invalid customization_t size, broken API" );
+STATIC_ASSERT( sizeof( resource_t ) == 136, "invalid resource_t size, broken API" );
+#else
+STATIC_ASSERT( sizeof( customization_t ) == 192, "invalid customization_t size, broken API" );
+STATIC_ASSERT( sizeof( resource_t ) == 144, "invalid resource_t size, broken API" );
+#endif
+
 #endif // CUSTOM_H