diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index f7d0afd..baad354 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -243,7 +243,7 @@ trap(struct trapframe *frame)
 	/*
 	 * A trap can occur while DTrace executes a probe. Before
 	 * executing the probe, DTrace blocks re-scheduling and sets
-	 * a flag in it's per-cpu flags to indicate that it doesn't
+	 * a flag in its per-cpu flags to indicate that it doesn't
 	 * want to fault. On returning from the probe, the no-fault
 	 * flag is cleared and finally re-scheduling is enabled.
 	 *
@@ -252,9 +252,18 @@ trap(struct trapframe *frame)
 	 * handled the trap and modified the trap frame so that this
 	 * function can return normally.
 	 */
-	if (type == T_DTRACE_RET || type == T_BPTFLT) {
+	if ((type == T_DTRACE_RET || type == T_BPTFLT) &&
+	    ISPL(frame->tf_cs) == SEL_UPL) {
 		struct reg regs;
 
+		/*
+		 * Enable interrupts before calling any fasttrap handlers, since
+		 * they may need to write to a userland address. The handler for
+		 * usermode breakpoints enables interrupts as well, so there's
+		 * no harm in doing that here even if we don't match an enabled
+		 * probe.
+		 */
+		enable_intr();
 		fill_frame_regs(frame, &regs);
 		if (type == T_BPTFLT &&
 		    dtrace_pid_probe_ptr != NULL &&
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index 884e0f0..c91a2f9 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -262,7 +262,7 @@ trap(struct trapframe *frame)
 	/*
 	 * A trap can occur while DTrace executes a probe. Before
 	 * executing the probe, DTrace blocks re-scheduling and sets
-	 * a flag in it's per-cpu flags to indicate that it doesn't
+	 * a flag in its per-cpu flags to indicate that it doesn't
 	 * want to fault. On returning from the probe, the no-fault
 	 * flag is cleared and finally re-scheduling is enabled.
 	 *
@@ -271,9 +271,18 @@ trap(struct trapframe *frame)
 	 * handled the trap and modified the trap frame so that this
 	 * function can return normally.
 	 */
-	if (type == T_DTRACE_RET || type == T_BPTFLT) {
+	if ((type == T_DTRACE_RET || type == T_BPTFLT) &&
+	    ISPL(frame->tf_cs) == SEL_UPL) {
 		struct reg regs;
 
+		/*
+		 * Enable interrupts before calling any fasttrap handlers, since
+		 * they may need to write to a userland address. The handler for
+		 * usermode breakpoints enables interrupts as well, so there's
+		 * no harm in doing that here even if we don't match an enabled
+		 * probe.
+		 */
+		enable_intr();
 		fill_frame_regs(frame, &regs);
 		if (type == T_BPTFLT &&
 		    dtrace_pid_probe_ptr != NULL &&