diff --git a/xen/arch/arm/mmu/setup.c b/xen/arch/arm/mmu/setup.c
index d042f73597..8fb0157aff 100644
--- a/xen/arch/arm/mmu/setup.c
+++ b/xen/arch/arm/mmu/setup.c
@@ -59,7 +59,7 @@ DEFINE_BOOT_PAGE_TABLE(xen_fixmap);
 static DEFINE_PAGE_TABLES(xen_xenmap, XEN_NR_ENTRIES(2));
 
 /* Limits of the Xen heap */
-mfn_t directmap_mfn_start __read_mostly = INVALID_MFN_INITIALIZER;
+mfn_t directmap_mfn_start __read_mostly = INVALID_MFN;
 mfn_t directmap_mfn_end __read_mostly;
 vaddr_t directmap_virt_end __read_mostly;
 #ifdef CONFIG_ARM_64
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index e9ce182d06..4d3b8c2204 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -480,7 +480,7 @@ static void __init setup_frametable_mappings(paddr_t ps, paddr_t pe)
 static void __init setup_directmap_mappings(unsigned long base_mfn,
                                             unsigned long nr_mfns)
 {
-    static mfn_t __initdata directmap_mfn_start = INVALID_MFN_INITIALIZER;
+    static mfn_t __initdata directmap_mfn_start = INVALID_MFN;
 
     mfn_t base_mfn_t = _mfn(base_mfn);
     unsigned long base_addr = mfn_to_maddr(base_mfn_t);
diff --git a/xen/arch/x86/efi/runtime.h b/xen/arch/x86/efi/runtime.h
index 88ab5651e9..f92d7af95e 100644
--- a/xen/arch/x86/efi/runtime.h
+++ b/xen/arch/x86/efi/runtime.h
@@ -7,7 +7,7 @@
 #include <asm/mc146818rtc.h>
 
 #ifndef COMPAT
-mfn_t __read_mostly efi_l4_mfn = INVALID_MFN_INITIALIZER;
+mfn_t __read_mostly efi_l4_mfn = INVALID_MFN;
 
 void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t l4e)
 {
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 3672bda025..2ca7723e50 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -991,7 +991,9 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
          * guaranteeing that it won't fall in the middle of the
          * [xatp->gpfn, xatp->gpfn + xatp->size) range checked above.
          */
-        BUILD_BUG_ON(INVALID_GFN_RAW + 1);
+        if ( gfn_x(INVALID_GFN) + 1 )
+            BUILD_ERROR("bad INVALID_GFN");
+
         return -EOVERFLOW;
     }
 
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index e01ac3e99c..40b0f73563 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -275,7 +275,7 @@ static PAGE_LIST_HEAD(page_broken_list);
  * When !CONFIG_NUMA first_valid_mfn is non-static, for use by respective
  * stubs.
  */
-STATIC_IF(CONFIG_NUMA) mfn_t first_valid_mfn = INVALID_MFN_INITIALIZER;
+STATIC_IF(CONFIG_NUMA) mfn_t first_valid_mfn = INVALID_MFN;
 
 struct bootmem_region {
     unsigned long s, e; /* MFNs @s through @e-1 inclusive are free */
diff --git a/xen/include/xen/mm-frame.h b/xen/include/xen/mm-frame.h
index d973aec901..1402c20497 100644
--- a/xen/include/xen/mm-frame.h
+++ b/xen/include/xen/mm-frame.h
@@ -6,13 +6,7 @@
 
 TYPE_SAFE(unsigned long, mfn);
 #define PRI_mfn          "05lx"
-#define INVALID_MFN_RAW  (~0UL)
-#define INVALID_MFN      _mfn(INVALID_MFN_RAW)
-/*
- * To be used for global variable initialization. This workaround a bug
- * in GCC < 5.0.
- */
-#define INVALID_MFN_INITIALIZER { INVALID_MFN_RAW }
+#define INVALID_MFN      ((mfn_t){ ~0UL })
 
 #if 0
 #define mfn_t /* Grep fodder: mfn_t, _mfn() and mfn_x() are defined above */
@@ -42,13 +36,7 @@ static inline bool mfn_eq(mfn_t x, mfn_t y)
 
 TYPE_SAFE(unsigned long, gfn);
 #define PRI_gfn          "05lx"
-#define INVALID_GFN_RAW  (~0UL)
-#define INVALID_GFN      _gfn(INVALID_GFN_RAW)
-/*
- * To be used for global variable initialization. This workaround a bug
- * in GCC < 5.0 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64856
- */
-#define INVALID_GFN_INITIALIZER { INVALID_GFN_RAW }
+#define INVALID_GFN      ((gfn_t){ ~0UL })
 
 #if 0
 #define gfn_t /* Grep fodder: gfn_t, _gfn() and gfn_x() are defined above */