diff --git a/lib/dns/tests/acl_test.c b/lib/dns/tests/acl_test.c
index 056e6469d2..5e7c34dbea 100644
--- a/lib/dns/tests/acl_test.c
+++ b/lib/dns/tests/acl_test.c
@@ -15,8 +15,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
diff --git a/lib/dns/tests/db_test.c b/lib/dns/tests/db_test.c
index 07f0cd160a..6738a53a1f 100644
--- a/lib/dns/tests/db_test.c
+++ b/lib/dns/tests/db_test.c
@@ -15,8 +15,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <unistd.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/dns/tests/dbdiff_test.c b/lib/dns/tests/dbdiff_test.c
index d310e784d0..1306bf8ac0 100644
--- a/lib/dns/tests/dbdiff_test.c
+++ b/lib/dns/tests/dbdiff_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/dbiterator_test.c b/lib/dns/tests/dbiterator_test.c
index 374f248f0a..e825b7b4d2 100644
--- a/lib/dns/tests/dbiterator_test.c
+++ b/lib/dns/tests/dbiterator_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/dbversion_test.c b/lib/dns/tests/dbversion_test.c
index 5cb0f0446c..79272735ca 100644
--- a/lib/dns/tests/dbversion_test.c
+++ b/lib/dns/tests/dbversion_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/dh_test.c b/lib/dns/tests/dh_test.c
index 8c2267dc22..6893aee1a6 100644
--- a/lib/dns/tests/dh_test.c
+++ b/lib/dns/tests/dh_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/dispatch_test.c b/lib/dns/tests/dispatch_test.c
index bfc0bd343f..9785fbfbae 100644
--- a/lib/dns/tests/dispatch_test.c
+++ b/lib/dns/tests/dispatch_test.c
@@ -16,6 +16,7 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/dnstap_test.c b/lib/dns/tests/dnstap_test.c
index f28e149a8b..da71a6c546 100644
--- a/lib/dns/tests/dnstap_test.c
+++ b/lib/dns/tests/dnstap_test.c
@@ -16,6 +16,7 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/dnstest.c b/lib/dns/tests/dnstest.c
index cf4d35f7a3..ce83df60a2 100644
--- a/lib/dns/tests/dnstest.c
+++ b/lib/dns/tests/dnstest.c
@@ -16,9 +16,10 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
-#include <string.h>
 #include <stdlib.h>
+#include <string.h>
 #include <time.h>
 #include <unistd.h>
 
diff --git a/lib/dns/tests/dst_test.c b/lib/dns/tests/dst_test.c
index 9809f5db77..0abe214520 100644
--- a/lib/dns/tests/dst_test.c
+++ b/lib/dns/tests/dst_test.c
@@ -15,8 +15,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #define UNIT_TESTING
diff --git a/lib/dns/tests/geoip_test.c b/lib/dns/tests/geoip_test.c
index a09f66e552..7481881a1e 100644
--- a/lib/dns/tests/geoip_test.c
+++ b/lib/dns/tests/geoip_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/keytable_test.c b/lib/dns/tests/keytable_test.c
index 1a92c2f2a2..c6f777f03a 100644
--- a/lib/dns/tests/keytable_test.c
+++ b/lib/dns/tests/keytable_test.c
@@ -15,10 +15,11 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
+#include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdio.h>
-#include <inttypes.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #define UNIT_TESTING
diff --git a/lib/dns/tests/master_test.c b/lib/dns/tests/master_test.c
index 73a0e64be2..cbf55f4942 100644
--- a/lib/dns/tests/master_test.c
+++ b/lib/dns/tests/master_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/lib/dns/tests/name_test.c b/lib/dns/tests/name_test.c
index 239c25d075..b3dcf81176 100644
--- a/lib/dns/tests/name_test.c
+++ b/lib/dns/tests/name_test.c
@@ -16,6 +16,7 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/nsec3_test.c b/lib/dns/tests/nsec3_test.c
index 7df028ddc1..8b43aadb0e 100644
--- a/lib/dns/tests/nsec3_test.c
+++ b/lib/dns/tests/nsec3_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/peer_test.c b/lib/dns/tests/peer_test.c
index 5ba37c831b..3ad5bc8274 100644
--- a/lib/dns/tests/peer_test.c
+++ b/lib/dns/tests/peer_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/private_test.c b/lib/dns/tests/private_test.c
index e8e642d1ba..7ea6ba61f7 100644
--- a/lib/dns/tests/private_test.c
+++ b/lib/dns/tests/private_test.c
@@ -16,6 +16,7 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/rbt_serialize_test.c b/lib/dns/tests/rbt_serialize_test.c
index 26894c9d7b..b4cd765e39 100644
--- a/lib/dns/tests/rbt_serialize_test.c
+++ b/lib/dns/tests/rbt_serialize_test.c
@@ -15,11 +15,12 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
-#include <inttypes.h>
 #include <fcntl.h>
-#include <unistd.h>
+#include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdlib.h>
 #include <sys/mman.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/dns/tests/rbt_test.c b/lib/dns/tests/rbt_test.c
index 158bf1dede..478ef68673 100644
--- a/lib/dns/tests/rbt_test.c
+++ b/lib/dns/tests/rbt_test.c
@@ -18,6 +18,7 @@
 #include <ctype.h>
 #include <fcntl.h>
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/rdata_test.c b/lib/dns/tests/rdata_test.c
index 0bf9779b7e..dc95ba6e26 100644
--- a/lib/dns/tests/rdata_test.c
+++ b/lib/dns/tests/rdata_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/rdataset_test.c b/lib/dns/tests/rdataset_test.c
index ec9bd929e7..bf9eee8c55 100644
--- a/lib/dns/tests/rdataset_test.c
+++ b/lib/dns/tests/rdataset_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/rdatasetstats_test.c b/lib/dns/tests/rdatasetstats_test.c
index 39c6f87a4d..53e518229b 100644
--- a/lib/dns/tests/rdatasetstats_test.c
+++ b/lib/dns/tests/rdatasetstats_test.c
@@ -16,6 +16,7 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/resolver_test.c b/lib/dns/tests/resolver_test.c
index df26b6c0dd..3d34e9fd4f 100644
--- a/lib/dns/tests/resolver_test.c
+++ b/lib/dns/tests/resolver_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <unistd.h>
 
diff --git a/lib/dns/tests/rsa_test.c b/lib/dns/tests/rsa_test.c
index 3b0433ec3d..d0dcb8992d 100644
--- a/lib/dns/tests/rsa_test.c
+++ b/lib/dns/tests/rsa_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/dns/tests/sigs_test.c b/lib/dns/tests/sigs_test.c
index 065f5a98b3..45e68def58 100644
--- a/lib/dns/tests/sigs_test.c
+++ b/lib/dns/tests/sigs_test.c
@@ -15,8 +15,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <string.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 
 #define UNIT_TESTING
diff --git a/lib/dns/tests/time_test.c b/lib/dns/tests/time_test.c
index f4b152562c..c1c0362021 100644
--- a/lib/dns/tests/time_test.c
+++ b/lib/dns/tests/time_test.c
@@ -15,9 +15,10 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
-#include <stdio.h>
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #define UNIT_TESTING
diff --git a/lib/dns/tests/tkey_test.c b/lib/dns/tests/tkey_test.c
index 8727f1eddd..f78cb2e6ae 100644
--- a/lib/dns/tests/tkey_test.c
+++ b/lib/dns/tests/tkey_test.c
@@ -12,10 +12,13 @@
 #if HAVE_CMOCKA
 
 #include <stdarg.h>
-#include <stdbool.h>
 #include <stddef.h>
-#include <stdlib.h>
 #include <setjmp.h>
+
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdbool.h>
+#include <stdlib.h>
+
 #include <cmocka.h>
 
 #include <isc/mem.h>
diff --git a/lib/dns/tests/tsig_test.c b/lib/dns/tests/tsig_test.c
index 0092a9be51..c489fcfeff 100644
--- a/lib/dns/tests/tsig_test.c
+++ b/lib/dns/tests/tsig_test.c
@@ -15,8 +15,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #define UNIT_TESTING
diff --git a/lib/dns/tests/update_test.c b/lib/dns/tests/update_test.c
index 168d1be99e..9798ccf192 100644
--- a/lib/dns/tests/update_test.c
+++ b/lib/dns/tests/update_test.c
@@ -15,11 +15,12 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <stdlib.h>
-#include <stdio.h>
 #include <inttypes.h>
-#include <unistd.h>
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdio.h>
+#include <stdlib.h>
 #include <time.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/dns/tests/zonemgr_test.c b/lib/dns/tests/zonemgr_test.c
index 59471f1e8f..2ab5c66ab3 100644
--- a/lib/dns/tests/zonemgr_test.c
+++ b/lib/dns/tests/zonemgr_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/dns/tests/zt_test.c b/lib/dns/tests/zt_test.c
index d558c2957f..ede2977341 100644
--- a/lib/dns/tests/zt_test.c
+++ b/lib/dns/tests/zt_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/irs/tests/resconf_test.c b/lib/irs/tests/resconf_test.c
index 2d4b6e80ef..81b601d52a 100644
--- a/lib/irs/tests/resconf_test.c
+++ b/lib/irs/tests/resconf_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/isc/tests/buffer_test.c b/lib/isc/tests/buffer_test.c
index 83aba23a16..80d01e04e4 100644
--- a/lib/isc/tests/buffer_test.c
+++ b/lib/isc/tests/buffer_test.c
@@ -17,6 +17,7 @@
 
 #include <fcntl.h>
 #include <limits.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/isc/tests/counter_test.c b/lib/isc/tests/counter_test.c
index 424ddf2821..6770dd2453 100644
--- a/lib/isc/tests/counter_test.c
+++ b/lib/isc/tests/counter_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/lib/isc/tests/heap_test.c b/lib/isc/tests/heap_test.c
index b29b441caa..9cc043152a 100644
--- a/lib/isc/tests/heap_test.c
+++ b/lib/isc/tests/heap_test.c
@@ -17,8 +17,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <string.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
+#include <string.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/hmac_test.c b/lib/isc/tests/hmac_test.c
index b86e8d5b54..9e49baffcb 100644
--- a/lib/isc/tests/hmac_test.c
+++ b/lib/isc/tests/hmac_test.c
@@ -16,8 +16,9 @@
 #include <stdarg.h>
 #include <stddef.h>
 #include <setjmp.h>
-#include <stdlib.h>
 
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdlib.h>
 #include <string.h>
 
 #define UNIT_TESTING
diff --git a/lib/isc/tests/ht_test.c b/lib/isc/tests/ht_test.c
index b712187ad0..ff7446cce1 100644
--- a/lib/isc/tests/ht_test.c
+++ b/lib/isc/tests/ht_test.c
@@ -16,6 +16,7 @@
 #include <setjmp.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/isc/tests/lex_test.c b/lib/isc/tests/lex_test.c
index 42b53020bf..ab44d15162 100644
--- a/lib/isc/tests/lex_test.c
+++ b/lib/isc/tests/lex_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/isc/tests/mem_test.c b/lib/isc/tests/mem_test.c
index eea3eed7cd..293ba3fcd3 100644
--- a/lib/isc/tests/mem_test.c
+++ b/lib/isc/tests/mem_test.c
@@ -15,9 +15,10 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <fcntl.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <unistd.h>
-#include <fcntl.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/parse_test.c b/lib/isc/tests/parse_test.c
index 2db2684dbd..60dfa188e4 100644
--- a/lib/isc/tests/parse_test.c
+++ b/lib/isc/tests/parse_test.c
@@ -17,11 +17,12 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
-#include <inttypes.h>
-#include <unistd.h>
 #include <time.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/pool_test.c b/lib/isc/tests/pool_test.c
index 20a0aaeed7..b902869b86 100644
--- a/lib/isc/tests/pool_test.c
+++ b/lib/isc/tests/pool_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/isc/tests/queue_test.c b/lib/isc/tests/queue_test.c
index f360ec9df4..c60e1e27b9 100644
--- a/lib/isc/tests/queue_test.c
+++ b/lib/isc/tests/queue_test.c
@@ -15,10 +15,11 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 #include <time.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/radix_test.c b/lib/isc/tests/radix_test.c
index 5af46a5851..5f49ac08fd 100644
--- a/lib/isc/tests/radix_test.c
+++ b/lib/isc/tests/radix_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/lib/isc/tests/random_test.c b/lib/isc/tests/random_test.c
index 18fcb3eb60..56f37ce025 100644
--- a/lib/isc/tests/random_test.c
+++ b/lib/isc/tests/random_test.c
@@ -24,6 +24,7 @@
 
 #include <inttypes.h>
 #include <math.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/lib/isc/tests/safe_test.c b/lib/isc/tests/safe_test.c
index 086c771508..92cfc8262e 100644
--- a/lib/isc/tests/safe_test.c
+++ b/lib/isc/tests/safe_test.c
@@ -17,8 +17,9 @@
 #include <stddef.h>
 #include <setjmp.h>
 
-#include <string.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
+#include <string.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/sockaddr_test.c b/lib/isc/tests/sockaddr_test.c
index 056ebd925a..64e3490ca4 100644
--- a/lib/isc/tests/sockaddr_test.c
+++ b/lib/isc/tests/sockaddr_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/isc/tests/socket_test.c b/lib/isc/tests/socket_test.c
index 35b33ea698..20cf26b22d 100644
--- a/lib/isc/tests/socket_test.c
+++ b/lib/isc/tests/socket_test.c
@@ -16,10 +16,11 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <time.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/symtab_test.c b/lib/isc/tests/symtab_test.c
index ef08a08010..fea0cda699 100644
--- a/lib/isc/tests/symtab_test.c
+++ b/lib/isc/tests/symtab_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/isc/tests/task_test.c b/lib/isc/tests/task_test.c
index 1043b4d1d4..9a0b902e22 100644
--- a/lib/isc/tests/task_test.c
+++ b/lib/isc/tests/task_test.c
@@ -15,11 +15,12 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
-#include <unistd.h>
-#include <inttypes.h>
 #include <string.h>
+#include <unistd.h>
 
 #define UNIT_TESTING
 #include <cmocka.h>
diff --git a/lib/isc/tests/taskpool_test.c b/lib/isc/tests/taskpool_test.c
index 1355a9268e..a7453d96e8 100644
--- a/lib/isc/tests/taskpool_test.c
+++ b/lib/isc/tests/taskpool_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/isc/tests/time_test.c b/lib/isc/tests/time_test.c
index 61a1792ba4..122997c8b8 100644
--- a/lib/isc/tests/time_test.c
+++ b/lib/isc/tests/time_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/isc/tests/timer_test.c b/lib/isc/tests/timer_test.c
index 31e0cf55f3..d2fa9fcbea 100644
--- a/lib/isc/tests/timer_test.c
+++ b/lib/isc/tests/timer_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
diff --git a/lib/isccfg/tests/parser_test.c b/lib/isccfg/tests/parser_test.c
index 75bb474589..d684c6b268 100644
--- a/lib/isccfg/tests/parser_test.c
+++ b/lib/isccfg/tests/parser_test.c
@@ -15,6 +15,7 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/lib/ns/tests/listenlist_test.c b/lib/ns/tests/listenlist_test.c
index a0aecd7707..5d4fd8763e 100644
--- a/lib/ns/tests/listenlist_test.c
+++ b/lib/ns/tests/listenlist_test.c
@@ -13,9 +13,11 @@
 
 #include <stdarg.h>
 #include <stddef.h>
-#include <stdlib.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdlib.h>
+
 #include <isc/util.h>
 
 #include <stdio.h>
diff --git a/lib/ns/tests/notify_test.c b/lib/ns/tests/notify_test.c
index de5433680e..1094c26391 100644
--- a/lib/ns/tests/notify_test.c
+++ b/lib/ns/tests/notify_test.c
@@ -13,9 +13,11 @@
 
 #include <stdarg.h>
 #include <stddef.h>
-#include <stdlib.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdlib.h>
+
 #include <isc/util.h>
 
 #include <stdio.h>
diff --git a/lib/ns/tests/plugin_test.c b/lib/ns/tests/plugin_test.c
index 8a7e207ca4..de910a9bd9 100644
--- a/lib/ns/tests/plugin_test.c
+++ b/lib/ns/tests/plugin_test.c
@@ -13,9 +13,11 @@
 
 #include <stdarg.h>
 #include <stddef.h>
-#include <stdlib.h>
 #include <setjmp.h>
 
+#include <sched.h> /* IWYU pragma: keep */
+#include <stdlib.h>
+
 #define UNIT_TESTING
 #include <cmocka.h>
 
diff --git a/lib/ns/tests/query_test.c b/lib/ns/tests/query_test.c
index 770c9f485e..bcbeecc167 100644
--- a/lib/ns/tests/query_test.c
+++ b/lib/ns/tests/query_test.c
@@ -18,6 +18,7 @@
 #include <isc/util.h>
 
 #include <inttypes.h>
+#include <sched.h> /* IWYU pragma: keep */
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>