diff --git a/src/basic/missing_loop.h b/src/basic/missing_loop.h
index f83a14c9149..56e46f0b8ac 100644
--- a/src/basic/missing_loop.h
+++ b/src/basic/missing_loop.h
@@ -26,10 +26,14 @@ assert_cc(LO_FLAGS_DIRECT_IO == 16);
 assert_cc(LOOP_SET_DIRECT_IO == 0x4C08);
 #endif
 
-#ifndef LOOP_SET_STATUS_SETTABLE_FLAGS
-#  define LOOP_SET_STATUS_SETTABLE_FLAGS (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN)
-#endif
-
 #ifndef LOOP_SET_BLOCK_SIZE
 #  define LOOP_SET_BLOCK_SIZE 0x4C09
+#else
+assert_cc(LOOP_SET_BLOCK_SIZE == 0x4C09);
+#endif
+
+#ifndef LOOP_SET_STATUS_SETTABLE_FLAGS
+#  define LOOP_SET_STATUS_SETTABLE_FLAGS (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN)
+#else
+assert_cc(LOOP_SET_STATUS_SETTABLE_FLAGS == (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN));
 #endif
diff --git a/src/fundamental/macro-fundamental.h b/src/fundamental/macro-fundamental.h
index 8aca5f784ae..bbfdcdb2187 100644
--- a/src/fundamental/macro-fundamental.h
+++ b/src/fundamental/macro-fundamental.h
@@ -517,9 +517,9 @@ static inline uint64_t ALIGN_OFFSET_U64(uint64_t l, uint64_t ali) {
                 }                                                       \
         }
 
-/* Restriction/bug (see above) was fixed in GCC 15 and clang 19.*/
+/* Restriction/bug (see below) was fixed in GCC 15 and clang 19. */
 #if __GNUC__ >= 15 || (defined(__clang__) && __clang_major__ >= 19)
-#define DECLARE_FLEX_ARRAY(type, name) type name[];
+#define DECLARE_FLEX_ARRAY(type, name) type name[]
 #else
 /* Declare a flexible array usable in a union.
  * This is essentially a work-around for a pointless constraint in C99
diff --git a/src/shared/selinux-util.h b/src/shared/selinux-util.h
index 038456fcca6..3a2cf0d8507 100644
--- a/src/shared/selinux-util.h
+++ b/src/shared/selinux-util.h
@@ -14,9 +14,8 @@
 
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(char*, freecon, NULL);
 #else
-static inline char* freeconp(char **p) {
+static inline void freeconp(char **p) {
         assert(*p == NULL);
-        return NULL;
 }
 #endif