diff --git a/src/cmd/go/internal/cache/default.go b/src/cmd/go/internal/cache/default.go
index f545c14..7d389c3 100644
--- a/src/cmd/go/internal/cache/default.go
+++ b/src/cmd/go/internal/cache/default.go
@@ -37,7 +37,7 @@
 // the first time Default is called.
 func initDefaultCache() {
 	dir := DefaultDir()
-	if dir == "off" || dir == "" {
+	if dir == "off" {
 		if defaultDirErr != nil {
 			base.Fatalf("build cache is required, but could not be located: %v", defaultDirErr)
 		}
@@ -74,7 +74,12 @@
 
 	defaultDirOnce.Do(func() {
 		defaultDir = os.Getenv("GOCACHE")
+		if filepath.IsAbs(defaultDir) || defaultDir == "off" {
+			return
+		}
 		if defaultDir != "" {
+			defaultDir = "off"
+			defaultDirErr = fmt.Errorf("GOCACHE is not an absolute path")
 			return
 		}
 
diff --git a/src/cmd/go/testdata/script/build_nocache.txt b/src/cmd/go/testdata/script/build_nocache.txt
index 5aa46e0..d1b12f4 100644
--- a/src/cmd/go/testdata/script/build_nocache.txt
+++ b/src/cmd/go/testdata/script/build_nocache.txt
@@ -10,6 +10,11 @@
 ! go build -o triv triv.go
 stderr 'build cache is required, but could not be located: GOCACHE is not defined and .*'
 
+# If GOCACHE is set but is not an absolute path, and we cannot build.
+env GOCACHE=test
+! go build -o triv triv.go
+stderr 'build cache is required, but could not be located: GOCACHE is not an absolute path'
+
 # An explicit GOCACHE=off also disables builds.
 env GOCACHE=off
 ! go build -o triv triv.go