diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 2a817f3d9a..ad2499701f 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -60,7 +60,7 @@ static void
 addexp(char *s)
 {
 	int i;
-
+	
 	for(i=0; exper[i].name != nil; i++) {
 		if(strcmp(exper[i].name, s) == 0) {
 			*exper[i].val = 1;
@@ -77,9 +77,7 @@ setexp(void)
 {
 	char *f[20];
 	int i, nf;
-
-	precisestack_enabled = 1; // on by default
-
+	
 	// The makefile #defines GOEXPERIMENT for us.
 	nf = getfields(GOEXPERIMENT, f, nelem(f), 1, ",");
 	for(i=0; i<nf; i++)
diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index ba31c503ee..b782d0fe1a 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -144,7 +144,7 @@ runtime·schedinit(void)
 	Eface i;
 
 	runtime·sched.maxmcount = 10000;
-	runtime·precisestack = true; // haveexperiment("precisestack");
+	runtime·precisestack = haveexperiment("precisestack");
 
 	runtime·mallocinit();
 	mcommoninit(m);