diff --git a/lib/Whateverable.pm6 b/lib/Whateverable.pm6
index 0639343..83a8e2d 100644
--- a/lib/Whateverable.pm6
+++ b/lib/Whateverable.pm6
@@ -377,7 +377,10 @@ sub test-delay {
     use NativeCall;
     sub kill(int32, int32) is native {*};
     sub getppid(--> int32) is native {*};
-    kill getppid, 10; # SIGUSR1
+    my $sig-compat = SIGUSR1;
+    # ↓ Fragile platform-specific hack
+    $sig-compat = 10 if $*PERL.compiler.version ≤ v2018.05;
+    kill getppid, +$sig-compat; # SIGUSR1
 }
 
 sub run-smth($full-commit-hash, $code, :$backend=‘rakudo-moar’) is export {
diff --git a/t/lib/Testable.pm6 b/t/lib/Testable.pm6
index 46480e5..8915fd6 100644
--- a/t/lib/Testable.pm6
+++ b/t/lib/Testable.pm6
@@ -22,7 +22,11 @@ class Testable {
         $!bot = $bot;
         my $ready  = Channel.new;
         $!messages = Channel.new;
-        $!delay-channel = signal(SIGUSR1).Channel;
+
+        my $sig-compat = SIGUSR1;
+        # ↓ Fragile platform-specific hack
+        $sig-compat = SIGBUS if v2018.04 ≤ $*PERL.compiler.version ≤ v2018.05;
+        $!delay-channel = signal($sig-compat).Channel;
 
         use Whateverable::Builds;
         ensure-cloned-repos;