diff --git a/go/ssa/interp/external.go b/go/ssa/interp/external.go
index 181ffa4194..f428e58d52 100644
--- a/go/ssa/interp/external.go
+++ b/go/ssa/interp/external.go
@@ -139,6 +139,7 @@ func init() {
 		"sync/atomic.StoreInt64":           ext۰atomic۰StoreInt64,
 		"sync/atomic.StoreUint64":          ext۰atomic۰StoreUint64,
 		"testing.callerEntry":              ext۰testing۰callerEntry,
+		"testing.callerName":               ext۰testing۰callerName,
 		"testing.runExample":               ext۰testing۰runExample,
 		"time.Sleep":                       ext۰time۰Sleep,
 		"time.now":                         ext۰time۰now,
@@ -527,10 +528,19 @@ func ext۰testing۰runExample(fr *frame, args []value) value {
 	return true
 }
 
+// These two internal functions must be faked to avoid calls to
+// runtime.CallersFrames, which is hard to emulate. We are inching
+// towards the point at which I blow away this entire package, or at
+// least all tests that interpret the standard "testing" package.
+
 func ext۰testing۰callerEntry(fr *frame, args []value) value {
 	return uintptr(0) // bogus implementation for now
 }
 
+func ext۰testing۰callerName(fr *frame, args []value) value {
+	return "<unknown>" // bogus implementation for now
+}
+
 func ext۰time۰now(fr *frame, args []value) value {
 	nano := time.Now().UnixNano()
 	return tuple{int64(nano / 1e9), int32(nano % 1e9), int64(0)}