diff --git a/dev-lang/python/python-3.10.0_alpha4.ebuild b/dev-lang/python/python-3.10.0_alpha4.ebuild
index a07c3376effdc..a68e95cd0c12b 100644
--- a/dev-lang/python/python-3.10.0_alpha4.ebuild
+++ b/dev-lang/python/python-3.10.0_alpha4.ebuild
@@ -186,6 +186,12 @@ src_configure() {
 	)
 
 	OPT="" econf "${myeconfargs[@]}"
+
+	if grep -q "#define POSIX_SEMAPHORES_NOT_ENABLED 1" pyconfig.h; then
+		eerror "configure has detected that the sem_open function is broken."
+		eerror "Please ensure that /dev/shm is mounted as a tmpfs with mode 1777."
+		die "Broken sem_open function (bug 496328)"
+	fi
 }
 
 src_compile() {