diff --git a/src/include/c.h b/src/include/c.h
index af799dc1df..4f8bbfcd62 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -343,6 +343,11 @@ typedef unsigned PG_INT128_TYPE uint128;
 #define PG_INT64_MAX	INT64CONST(0x7FFFFFFFFFFFFFFF)
 #define PG_UINT64_MAX	UINT64CONST(0xFFFFFFFFFFFFFFFF)
 
+/* Max value of size_t might also be missing if we don't have stdint.h */
+#ifndef SIZE_MAX
+#define SIZE_MAX ((size_t) -1)
+#endif
+
 /*
  * We now always use int64 timestamps, but keep this symbol defined for the
  * benefit of external code that might test it.
diff --git a/src/include/utils/memutils.h b/src/include/utils/memutils.h
index c553349066..869c59dc85 100644
--- a/src/include/utils/memutils.h
+++ b/src/include/utils/memutils.h
@@ -41,7 +41,7 @@
 
 #define AllocSizeIsValid(size)	((Size) (size) <= MaxAllocSize)
 
-#define MaxAllocHugeSize	((Size) -1 >> 1)	/* SIZE_MAX / 2 */
+#define MaxAllocHugeSize	(SIZE_MAX / 2)
 
 #define AllocHugeSizeIsValid(size)	((Size) (size) <= MaxAllocHugeSize)
 
diff --git a/src/timezone/private.h b/src/timezone/private.h
index c141fb6131..e65cd1bb4e 100644
--- a/src/timezone/private.h
+++ b/src/timezone/private.h
@@ -48,10 +48,6 @@
 /* Unlike <ctype.h>'s isdigit, this also works if c < 0 | c > UCHAR_MAX. */
 #define is_digit(c) ((unsigned)(c) - '0' <= 9)
 
-#ifndef SIZE_MAX
-#define SIZE_MAX ((size_t) -1)
-#endif
-
 /*
  * SunOS 4.1.1 libraries lack remove.
  */