diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index d6447caff69..bbadad1bed9 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -573,8 +573,9 @@ func (p *Package) writeExports(fgo2, fc, fm *os.File) {
 			goname = "_cgoexpwrap" + cPrefix + "_" + fn.Recv.List[0].Names[0].Name + "_" + goname
 		}
 		fmt.Fprintf(fc, "#pragma dynexport %s %s\n", goname, goname)
-		fmt.Fprintf(fc, "extern void ·%s();\n", goname)
-		fmt.Fprintf(fc, "\nvoid\n")
+		fmt.Fprintf(fc, "extern void ·%s();\n\n", goname)
+		fmt.Fprintf(fc, "#pragma textflag 7\n") // no split stack, so no use of m or g
+		fmt.Fprintf(fc, "void\n")
 		fmt.Fprintf(fc, "_cgoexp%s_%s(void *a, int32 n)\n", cPrefix, exp.ExpName)
 		fmt.Fprintf(fc, "{\n")
 		fmt.Fprintf(fc, "\truntime·cgocallback(·%s, a, n);\n", goname)
diff --git a/src/pkg/runtime/asm_386.s b/src/pkg/runtime/asm_386.s
index 6bbec30638b..da2290210a4 100644
--- a/src/pkg/runtime/asm_386.s
+++ b/src/pkg/runtime/asm_386.s
@@ -425,6 +425,14 @@ TEXT runtime·cgocallback(SB),7,$12
 	// Save current m->g0->sched.sp on stack and then set it to SP.
 	get_tls(CX)
 	MOVL	m(CX), BP
+
+	// If m is nil, it is almost certainly because we have been called
+	// on a thread that Go did not create.  We're going to crash as
+	// soon as we try to use m; instead, try to print a nice error and exit.
+	CMPL	BP, $0
+	JNE 2(PC)
+	CALL	runtime·badcallback(SB)
+
 	MOVL	m_g0(BP), SI
 	PUSHL	(g_sched+gobuf_sp)(SI)
 	MOVL	SP, (g_sched+gobuf_sp)(SI)
diff --git a/src/pkg/runtime/asm_amd64.s b/src/pkg/runtime/asm_amd64.s
index 2ea87a779f4..392ad8c87fa 100644
--- a/src/pkg/runtime/asm_amd64.s
+++ b/src/pkg/runtime/asm_amd64.s
@@ -471,6 +471,14 @@ TEXT runtime·cgocallback(SB),7,$24
 	// Save current m->g0->sched.sp on stack and then set it to SP.
 	get_tls(CX)
 	MOVQ	m(CX), BP
+	
+	// If m is nil, it is almost certainly because we have been called
+	// on a thread that Go did not create.  We're going to crash as
+	// soon as we try to use m; instead, try to print a nice error and exit.
+	CMPQ	BP, $0
+	JNE 2(PC)
+	CALL	runtime·badcallback(SB)
+
 	MOVQ	m_g0(BP), SI
 	PUSHQ	(g_sched+gobuf_sp)(SI)
 	MOVQ	SP, (g_sched+gobuf_sp)(SI)
diff --git a/src/pkg/runtime/thread_darwin.c b/src/pkg/runtime/thread_darwin.c
index 556fb67e842..bbcdf05ef01 100644
--- a/src/pkg/runtime/thread_darwin.c
+++ b/src/pkg/runtime/thread_darwin.c
@@ -477,3 +477,13 @@ runtime·setprof(bool on)
 	else
 		runtime·sigprocmask(SIG_BLOCK, &sigset_prof, nil);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	runtime·write(2, badcallback, sizeof badcallback - 1);
+}
diff --git a/src/pkg/runtime/thread_freebsd.c b/src/pkg/runtime/thread_freebsd.c
index 77e8bb3dac3..b848cbadd44 100644
--- a/src/pkg/runtime/thread_freebsd.c
+++ b/src/pkg/runtime/thread_freebsd.c
@@ -195,3 +195,13 @@ runtime·setprof(bool on)
 {
 	USED(on);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	runtime·write(2, badcallback, sizeof badcallback - 1);
+}
diff --git a/src/pkg/runtime/thread_linux.c b/src/pkg/runtime/thread_linux.c
index 6b428440e01..af765d53b93 100644
--- a/src/pkg/runtime/thread_linux.c
+++ b/src/pkg/runtime/thread_linux.c
@@ -255,3 +255,13 @@ runtime·setprof(bool on)
 {
 	USED(on);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	runtime·write(2, badcallback, sizeof badcallback - 1);
+}
diff --git a/src/pkg/runtime/thread_netbsd.c b/src/pkg/runtime/thread_netbsd.c
index 62e133c449b..40e4f6ce1c6 100644
--- a/src/pkg/runtime/thread_netbsd.c
+++ b/src/pkg/runtime/thread_netbsd.c
@@ -213,3 +213,13 @@ runtime·setprof(bool on)
 {
 	USED(on);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	runtime·write(2, badcallback, sizeof badcallback - 1);
+}
diff --git a/src/pkg/runtime/thread_openbsd.c b/src/pkg/runtime/thread_openbsd.c
index bee0c5755fa..e4f95988b0a 100644
--- a/src/pkg/runtime/thread_openbsd.c
+++ b/src/pkg/runtime/thread_openbsd.c
@@ -213,3 +213,13 @@ runtime·setprof(bool on)
 {
 	USED(on);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	runtime·write(2, badcallback, sizeof badcallback - 1);
+}
diff --git a/src/pkg/runtime/thread_plan9.c b/src/pkg/runtime/thread_plan9.c
index aaed5050bb8..4ca01b0e668 100644
--- a/src/pkg/runtime/thread_plan9.c
+++ b/src/pkg/runtime/thread_plan9.c
@@ -247,3 +247,13 @@ runtime·setprof(bool on)
 {
 	USED(on);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	runtime·pwrite(2, badcallback, sizeof badcallback - 1, -1LL);
+}
diff --git a/src/pkg/runtime/thread_windows.c b/src/pkg/runtime/thread_windows.c
index 1147a05e6a3..e75e0c1569e 100644
--- a/src/pkg/runtime/thread_windows.c
+++ b/src/pkg/runtime/thread_windows.c
@@ -422,3 +422,22 @@ runtime·setprof(bool on)
 {
 	USED(on);
 }
+
+static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
+
+// This runs on a foreign stack, without an m or a g.  No stack split.
+#pragma textflag 7
+void
+runtime·badcallback(void)
+{
+	uint32 written;
+
+	runtime·stdcall(
+		runtime·WriteFile, 5,
+		runtime·stdcall(runtime·GetStdHandle, 1, (uintptr)-12), // stderr
+		badcallback,
+		(uintptr)(sizeof badcallback - 1),
+		&written,
+		nil
+	);
+}