diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index a9bf55bc4f95..9a5148b48480 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -744,6 +744,7 @@ sendsig(catcher, sig, mask, code)
 	regs->tf_cs = _ucodesel;
 	regs->tf_ds = _udatasel;
 	regs->tf_es = _udatasel;
+	regs->tf_fs = _udatasel;
 	regs->tf_ss = _udatasel;
 }
 
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index a9bf55bc4f95..9a5148b48480 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -744,6 +744,7 @@ sendsig(catcher, sig, mask, code)
 	regs->tf_cs = _ucodesel;
 	regs->tf_ds = _udatasel;
 	regs->tf_es = _udatasel;
+	regs->tf_fs = _udatasel;
 	regs->tf_ss = _udatasel;
 }