diff --git a/src/pkg/crypto/rand/rand_unix.go b/src/pkg/crypto/rand/rand_unix.go
index d8db6f2a04..ff16f25547 100644
--- a/src/pkg/crypto/rand/rand_unix.go
+++ b/src/pkg/crypto/rand/rand_unix.go
@@ -32,6 +32,7 @@ func (r *devReader) Read(b []byte) (n int, err os.Error) {
 	if r.f == nil {
 		f, err := os.Open(r.name, os.O_RDONLY, 0)
 		if f == nil {
+			r.mu.Unlock()
 			return 0, err
 		}
 		r.f = f
diff --git a/src/pkg/crypto/rand/rand_windows.go b/src/pkg/crypto/rand/rand_windows.go
index 9bab2cba88..4b2b7a26f3 100755
--- a/src/pkg/crypto/rand/rand_windows.go
+++ b/src/pkg/crypto/rand/rand_windows.go
@@ -30,6 +30,7 @@ func (r *rngReader) Read(b []byte) (n int, err os.Error) {
 		const flags = syscall.CRYPT_VERIFYCONTEXT | syscall.CRYPT_SILENT
 		ok, errno := syscall.CryptAcquireContext(&r.prov, nil, nil, provType, flags)
 		if !ok {
+			r.mu.Unlock()
 			return 0, os.NewSyscallError("CryptAcquireContext", errno)
 		}
 	}