diff --git a/src/runtime/testdata/testprogcgo/threadpprof.go b/src/runtime/testdata/testprogcgo/threadpprof.go
index 44afb91d96f..3da82961b9b 100644
--- a/src/runtime/testdata/testprogcgo/threadpprof.go
+++ b/src/runtime/testdata/testprogcgo/threadpprof.go
@@ -61,7 +61,7 @@ static void* cpuHogDriver(void* arg __attribute__ ((unused))) {
 	return 0;
 }
 
-void runCPUHogThread() {
+void runCPUHogThread(void) {
 	pthread_t tid;
 	pthread_create(&tid, 0, cpuHogDriver, 0);
 }
diff --git a/src/runtime/testdata/testprogcgo/traceback.go b/src/runtime/testdata/testprogcgo/traceback.go
index e8b0a04556a..2a023f66cae 100644
--- a/src/runtime/testdata/testprogcgo/traceback.go
+++ b/src/runtime/testdata/testprogcgo/traceback.go
@@ -15,16 +15,16 @@ package main
 
 char *p;
 
-static int f3() {
+static int f3(void) {
 	*p = 0;
 	return 0;
 }
 
-static int f2() {
+static int f2(void) {
 	return f3();
 }
 
-static int f1() {
+static int f1(void) {
 	return f2();
 }