diff --git a/system/libuv/CMakeLists.txt b/system/libuv/CMakeLists.txt
index 12cde4fa7..5364fb959 100644
--- a/system/libuv/CMakeLists.txt
+++ b/system/libuv/CMakeLists.txt
@@ -171,6 +171,13 @@ if(CONFIG_LIBUV)
         ${LIBUV_TEST_DIR}/run-tests.c ${LIBUV_TEST_DIR}/runner.c
         ${LIBUV_TEST_DIR}/runner-unix.c ${LIBUV_TEST_DIR}/echo-server.c)
     file(GLOB TEST_CSRCS ${LIBUV_TEST_DIR}/test-*.c)
+
+    # See system/libuv/Makefile.
+
+    if(NOT CONFIG_ARCH_HAVE_FORK)
+      list(REMOVE_ITEM TEST_CSRCS ${LIBUV_TEST_DIR}/test-fork.c
+           ${LIBUV_TEST_DIR}/test-pipe-close-stdout-read-stdin.c)
+    endif()
     list(APPEND LIBUV_UTILS_TEST_SRCS ${TEST_CSRCS})
     nuttx_add_application(
       NAME
diff --git a/system/libuv/Makefile b/system/libuv/Makefile
index dec76cc1a..483f6194f 100644
--- a/system/libuv/Makefile
+++ b/system/libuv/Makefile
@@ -144,7 +144,19 @@ CSRCS += runner.c
 CSRCS += runner-unix.c
 CSRCS += echo-server.c
 
-CSRCS += $(wildcard libuv/test/test-*.c)
+LIBUV_TEST_CSRCS  = $(wildcard libuv/test/test-*.c)
+
+# test-fork.c and test-pipe-close-stdout-read-stdin.c call fork(), so they
+# cannot be built where NuttX does not provide it.  Nothing is lost either
+# way: every test they define is already excluded from the task list on
+# NuttX by 0001-libuv-port-for-nuttx.patch.
+
+ifeq ($(CONFIG_ARCH_HAVE_FORK),)
+LIBUV_TEST_CSRCS := $(filter-out libuv/test/test-fork.c,$(LIBUV_TEST_CSRCS))
+LIBUV_TEST_CSRCS := $(filter-out libuv/test/test-pipe-close-stdout-read-stdin.c,$(LIBUV_TEST_CSRCS))
+endif
+
+CSRCS += $(LIBUV_TEST_CSRCS)
 endif
 
 ifneq ($(CONFIG_LIBUV_UTILS_BENCHMARK),)
diff --git a/testing/ltp/CMakeLists.txt b/testing/ltp/CMakeLists.txt
index 2e458d5e4..8d4674ecd 100644
--- a/testing/ltp/CMakeLists.txt
+++ b/testing/ltp/CMakeLists.txt
@@ -86,6 +86,12 @@ if(CONFIG_TESTING_LTP)
       list(APPEND BLACKWORDS "pthread_spin_init" "pthread_spin_destroy"
            "pthread_spin_trylock")
     endif()
+
+    # See testing/ltp/Makefile.
+
+    if(NOT CONFIG_ARCH_HAVE_FORK)
+      list(APPEND BLACKWORDS "[^v_]fork(")
+    endif()
     list(
       APPEND
       BLACKWORDS
diff --git a/testing/ltp/Makefile b/testing/ltp/Makefile
index 39a7d931b..cee750cd0 100644
--- a/testing/ltp/Makefile
+++ b/testing/ltp/Makefile
@@ -44,6 +44,13 @@ BLACKWORDS  += "pthread_spin_destroy"
 BLACKWORDS  += "pthread_spin_trylock"
 endif
 
+# Where NuttX does not declare fork(), a test that calls it cannot be built.
+# The pattern spares vfork() and task_fork(), which remain available.
+
+ifeq ($(CONFIG_ARCH_HAVE_FORK),)
+BLACKWORDS  += "[^v_]fork("
+endif
+
 BLACKWORDS  += "CHILD_MAX"
 BLACKWORDS  += "setpgid("
 BLACKWORDS  += "PTHREAD_SCOPE_PROCESS"