diff --git a/meson.build b/meson.build
index 7d9f2d3d4c..8b4458d205 100644
--- a/meson.build
+++ b/meson.build
@@ -3318,11 +3318,15 @@ custom_target(
                    '} >@OUTPUT@'],
         build_by_default : true)
 
-# We intentionally do not do inline initializations with definitions for
-# a bunch of _cleanup_ variables in tests, to ensure valgrind is triggered.
-# This triggers a lot of maybe-uninitialized false positives when the
-# combination of -O2 and -flto is used. Suppress them.
-no_uninit = '-O2' in get_option('c_args') and '-flto=auto' in get_option('c_args') ? cc.first_supported_argument('-Wno-maybe-uninitialized') : []
+test_cflags = ['-DTEST_CODE=1']
+# We intentionally do not do inline initializations with definitions for a
+# bunch of _cleanup_ variables in tests, to ensure valgrind is triggered if we
+# use the variable unexpectedly. This triggers a lot of maybe-uninitialized
+# false positives when the combination of -O2 and -flto is used. Suppress them.
+if '-O2' in get_option('c_args') and '-flto=auto' in get_option('c_args')
+        test_cflags += cc.first_supported_argument('-Wno-maybe-uninitialized')
+endif
+
 foreach tuple : tests
         sources = tuple[0]
         link_with = tuple.length() > 1 and tuple[1].length() > 0 ? tuple[1] : [libshared]
@@ -3331,7 +3335,7 @@ foreach tuple : tests
         condition = tuple.length() > 4 ? tuple[4] : ''
         type = tuple.length() > 5 ? tuple[5] : ''
         defs = tuple.length() > 6 ? tuple[6] : []
-        defs += no_uninit
+        defs += test_cflags
         parallel = tuple.length() > 7 ? tuple[7] : true
         timeout = 30
 
@@ -3399,7 +3403,7 @@ exe = executable(
         'test-libudev-sym',
         test_libudev_sym_c,
         include_directories : libudev_includes,
-        c_args : ['-Wno-deprecated-declarations'] + no_uninit,
+        c_args : ['-Wno-deprecated-declarations'] + test_cflags,
         link_with : [libudev],
         build_by_default : want_tests != 'false',
         install : install_tests,
@@ -3412,7 +3416,7 @@ exe = executable(
         'test-libudev-static-sym',
         test_libudev_sym_c,
         include_directories : libudev_includes,
-        c_args : ['-Wno-deprecated-declarations'] + no_uninit,
+        c_args : ['-Wno-deprecated-declarations'] + test_cflags,
         link_with : [install_libudev_static],
         build_by_default : want_tests != 'false' and static_libudev_pic,
         install : install_tests and static_libudev_pic,
@@ -3453,7 +3457,7 @@ foreach tuple : fuzzers
                 include_directories : [incs, include_directories('src/fuzz')],
                 link_with : link_with,
                 dependencies : dependencies,
-                c_args : defs,
+                c_args : defs + test_cflags,
                 link_args: link_args,
                 install : false,
                 build_by_default : fuzz_tests or fuzzer_build)
diff --git a/src/basic/log.h b/src/basic/log.h
index f7785b016b..9a57fcd0f1 100644
--- a/src/basic/log.h
+++ b/src/basic/log.h
@@ -189,7 +189,7 @@ void log_assert_failed_return(
         log_dispatch_internal(level, error, PROJECT_FILE, __LINE__, __func__, NULL, NULL, NULL, NULL, buffer)
 
 /* Logging with level */
-#define log_full_errno(level, error, ...)                               \
+#define log_full_errno_zerook(level, error, ...)                        \
         ({                                                              \
                 int _level = (level), _e = (error);                     \
                 _e = (log_get_max_level() >= LOG_PRI(_level))           \
@@ -198,17 +198,30 @@ void log_assert_failed_return(
                 _e < 0 ? _e : -EIO;                                     \
         })
 
+#if BUILD_MODE_DEVELOPER && !defined(TEST_CODE)
+#  define ASSERT_NON_ZERO(x) assert((x) != 0)
+#else
+#  define ASSERT_NON_ZERO(x)
+#endif
+
+#define log_full_errno(level, error, ...)                               \
+        ({                                                              \
+                int _error = (error);                                   \
+                ASSERT_NON_ZERO(_error);                                \
+                log_full_errno_zerook(level, _error, __VA_ARGS__);      \
+        })
+
 #define log_full(level, fmt, ...)                                      \
         ({                                                             \
                 if (BUILD_MODE_DEVELOPER)                              \
                         assert(!strstr(fmt, "%m"));                    \
-                (void) log_full_errno((level), 0, fmt, ##__VA_ARGS__); \
+                (void) log_full_errno_zerook(level, 0, fmt, ##__VA_ARGS__); \
         })
 
 int log_emergency_level(void);
 
 /* Normal logging */
-#define log_debug(...)     log_full_errno(LOG_DEBUG, 0, __VA_ARGS__)
+#define log_debug(...)     log_full_errno_zerook(LOG_DEBUG, 0, __VA_ARGS__)
 #define log_info(...)      log_full(LOG_INFO,    __VA_ARGS__)
 #define log_notice(...)    log_full(LOG_NOTICE,  __VA_ARGS__)
 #define log_warning(...)   log_full(LOG_WARNING, __VA_ARGS__)
diff --git a/src/shared/bus-wait-for-jobs.c b/src/shared/bus-wait-for-jobs.c
index e66c8beafa..8458fe8684 100644
--- a/src/shared/bus-wait-for-jobs.c
+++ b/src/shared/bus-wait-for-jobs.c
@@ -306,7 +306,8 @@ int bus_wait_for_jobs(BusWaitForJobs *d, bool quiet, const char* const* extra_ar
                         if (q < 0 && r == 0)
                                 r = q;
 
-                        log_debug_errno(q, "Got result %s/%m for job %s", d->result, d->name);
+                        log_full_errno_zerook(LOG_DEBUG, q,
+                                              "Got result %s/%m for job %s", d->result, d->name);
                 }
 
                 d->name = mfree(d->name);
diff --git a/src/test/test-bpf-foreign-programs.c b/src/test/test-bpf-foreign-programs.c
index e703924077..666317e520 100644
--- a/src/test/test-bpf-foreign-programs.c
+++ b/src/test/test-bpf-foreign-programs.c
@@ -293,7 +293,7 @@ int main(int argc, char *argv[]) {
 
         r = cg_all_unified();
         if (r <= 0)
-                return log_tests_skipped_errno(r, "Unified hierarchy is required, skipping.");
+                return log_tests_skipped("Unified hierarchy is required, skipping.");
 
         r = enter_cgroup_subroot(NULL);
         if (r == -ENOMEDIUM)