diff --git a/sys/arch/amd64/amd64/cpufunc.S b/sys/arch/amd64/amd64/cpufunc.S
index 9aa328a9df6a..1d78c4cf710e 100644
--- a/sys/arch/amd64/amd64/cpufunc.S
+++ b/sys/arch/amd64/amd64/cpufunc.S
@@ -398,11 +398,16 @@ ENTRY(x86_mwait)
 	ret
 END(x86_mwait)
 
+ENTRY(clts)
+	clts
+	jmp	_C_LABEL(stts_clts_record)
+END(clts)
+
 ENTRY(stts)
 	movq	%cr0, %rax
 	orq	$CR0_TS, %rax
 	movq	%rax, %cr0
-	ret
+	jmp	_C_LABEL(stts_clts_record)
 END(stts)
 
 ENTRY(fldummy)
diff --git a/sys/arch/i386/i386/cpufunc.S b/sys/arch/i386/i386/cpufunc.S
index 931f0962aa27..dc341c5ca622 100644
--- a/sys/arch/i386/i386/cpufunc.S
+++ b/sys/arch/i386/i386/cpufunc.S
@@ -297,6 +297,11 @@ ENTRY(x86_mwait)
 	ret
 END(x86_mwait)  
 
+ENTRY(clts)
+	clts
+	jmp	_C_LABEL(stts_clts_record)
+END(clts)
+
 ENTRY(stts)
 	movl	%cr0, %eax
 	testl	$CR0_TS, %eax
@@ -304,7 +309,7 @@ ENTRY(stts)
 	orl	$CR0_TS, %eax
 	movl	%eax, %cr0
 1:
-	ret
+	jmp	_C_LABEL(stts_clts_record)
 END(stts)
 
 ENTRY(fldummy)
diff --git a/sys/arch/x86/include/cpufunc.h b/sys/arch/x86/include/cpufunc.h
index 524b8db6d867..3d701fd86c2d 100644
--- a/sys/arch/x86/include/cpufunc.h
+++ b/sys/arch/x86/include/cpufunc.h
@@ -327,12 +327,7 @@ fnstsw(uint16_t *val)
 	);
 }
 
-static inline void
-clts(void)
-{
-	__asm volatile ("clts" ::: "memory");
-}
-
+void	clts(void);
 void	stts(void);
 
 static inline void
diff --git a/sys/arch/x86/x86/fpu.c b/sys/arch/x86/x86/fpu.c
index 6730a1febce7..5f0ae59f5e34 100644
--- a/sys/arch/x86/x86/fpu.c
+++ b/sys/arch/x86/x86/fpu.c
@@ -576,12 +576,49 @@ fputrap(struct trapframe *frame)
 	(*curlwp->l_proc->p_emul->e_trapsignal)(curlwp, &ksi);
 }
 
+static vaddr_t last_stts_clts[MAXCPUS];
+
+void stts_clts_record(void);
+void
+stts_clts_record(void)
+{
+
+	last_stts_clts[cpu_number()] = (vaddr_t)__builtin_return_address(0);
+}
+
+#include <sys/pserialize.h>
+#include <sys/ksyms.h>
+
 void
 fpudna(struct trapframe *frame)
 {
-	panic("fpudna from %s, ip %p, trapframe %p",
+	vaddr_t addr = last_stts_clts[cpu_number()];
+	const char *mod, *sym;
+	char buf[128];
+	int s;
+
+	s = pserialize_read_enter();
+	if (ksyms_getname(&mod, &sym, addr, KSYMS_PROC|KSYMS_CLOSEST) == 0) {
+		unsigned long naddr;
+		char offset[32];
+
+		if (ksyms_getval(mod, sym, &naddr, KSYMS_ANY) == 0 &&
+		    (addr - naddr) != 0) {
+			snprintf(offset, sizeof(offset), "+%p",
+			    (void *)(addr - naddr));
+		} else {
+			offset[0] = '\0';
+		}
+		snprintf(buf, sizeof(buf), "%s:%s%s", mod, sym, offset);
+	} else {
+		snprintf(buf, sizeof(buf), "%"PRIxVADDR, addr);
+	}
+	pserialize_read_exit(s);
+
+	panic("fpudna from %s, ip %p, trapframe %p, cr0 0x%"PRIxREGISTER","
+	    " last stts/clts %s",
 	    USERMODE(frame->tf_cs) ? "userland" : "kernel",
-	    (void *)X86_TF_RIP(frame), frame);
+	    (void *)X86_TF_RIP(frame), frame, rcr0(), buf);
 }
 
 /* -------------------------------------------------------------------------- */