diff --git a/src/include/c.h b/src/include/c.h
index c00a9ecf21d..631ead8db79 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1022,10 +1022,10 @@ pg_noreturn extern void ExceptionalCondition(const char *conditionName,
  */
 #ifdef HAVE__BUILTIN_TYPES_COMPATIBLE_P
 #define StaticAssertVariableIsOfType(varname, typename) \
-	StaticAssertDecl(__builtin_types_compatible_p(__typeof__(varname), typename), \
+	StaticAssertDecl(__builtin_types_compatible_p(typeof(varname), typename), \
 	CppAsString(varname) " does not have type " CppAsString(typename))
 #define StaticAssertVariableIsOfTypeMacro(varname, typename) \
-	(StaticAssertExpr(__builtin_types_compatible_p(__typeof__(varname), typename), \
+	(StaticAssertExpr(__builtin_types_compatible_p(typeof(varname), typename), \
 	 CppAsString(varname) " does not have type " CppAsString(typename)))
 #else							/* !HAVE__BUILTIN_TYPES_COMPATIBLE_P */
 #define StaticAssertVariableIsOfType(varname, typename) \
@@ -1289,11 +1289,11 @@ typedef struct PGAlignedXLogBlock PGAlignedXLogBlock;
 #define unvolatize(underlying_type, expr) const_cast<underlying_type>(expr)
 #elif defined(HAVE__BUILTIN_TYPES_COMPATIBLE_P)
 #define unconstify(underlying_type, expr) \
-	(StaticAssertExpr(__builtin_types_compatible_p(__typeof(expr), const underlying_type), \
+	(StaticAssertExpr(__builtin_types_compatible_p(typeof(expr), const underlying_type), \
 					  "wrong cast"), \
 	 (underlying_type) (expr))
 #define unvolatize(underlying_type, expr) \
-	(StaticAssertExpr(__builtin_types_compatible_p(__typeof(expr), volatile underlying_type), \
+	(StaticAssertExpr(__builtin_types_compatible_p(typeof(expr), volatile underlying_type), \
 					  "wrong cast"), \
 	 (underlying_type) (expr))
 #else