diff --git a/ssa/interp/external.go b/ssa/interp/external.go
index 8df7937ef0..391e909c91 100644
--- a/ssa/interp/external.go
+++ b/ssa/interp/external.go
@@ -67,6 +67,7 @@ var externals = map[string]externalFn{
 	"runtime.ReadMemStats":            ext۰runtime۰ReadMemStats,
 	"runtime.SetFinalizer":            ext۰runtime۰SetFinalizer,
 	"runtime.getgoroot":               ext۰runtime۰getgoroot,
+	"sync.runtime_Syncsemcheck":       ext۰sync۰runtime_Syncsemcheck,
 	"sync/atomic.AddInt32":            ext۰atomic۰AddInt32,
 	"sync/atomic.CompareAndSwapInt32": ext۰atomic۰CompareAndSwapInt32,
 	"sync/atomic.LoadInt32":           ext۰atomic۰LoadInt32,
@@ -150,6 +151,11 @@ func ext۰runtime۰getgoroot(fn *ssa.Function, args []value) value {
 	return os.Getenv("GOROOT")
 }
 
+func ext۰sync۰runtime_Syncsemcheck(fn *ssa.Function, args []value) value {
+	// TODO(adonovan): do equivalent of calling runtime_Syncsemcheck(size uintptr) here
+	return nil
+}
+
 func ext۰runtime۰GOMAXPROCS(fn *ssa.Function, args []value) value {
 	return runtime.GOMAXPROCS(args[0].(int))
 }