diff --git a/source/build/include/compat.h b/source/build/include/compat.h
index 9b1227bbb..38c479a46 100644
--- a/source/build/include/compat.h
+++ b/source/build/include/compat.h
@@ -129,6 +129,14 @@
 # define inline __inline
 #endif
 
+#ifndef MAY_ALIAS
+# ifdef _MSC_VER
+#  define MAY_ALIAS
+# else
+#  define MAY_ALIAS __attribute__((may_alias))
+# endif
+#endif
+
 #ifndef FORCE_INLINE
 # ifdef _MSC_VER
 #  define FORCE_INLINE __forceinline
@@ -783,7 +791,7 @@ typedef reg_t unative_t;
 #endif
 EDUKE32_STATIC_ASSERT(sizeof(native_t) == sizeof(unative_t));
 
-typedef struct {
+typedef struct MAY_ALIAS {
     int32_t x, y;
 } vec2_t;
 
@@ -795,7 +803,7 @@ typedef struct {
     uint32_t x, y;
 } vec2u_t;
 
-typedef struct {
+typedef struct MAY_ALIAS {
     int32_t x, y, z;
 } vec3_t;