diff --git a/basepath.go b/basepath.go
index 3434137..4b325ed 100644
--- a/basepath.go
+++ b/basepath.go
@@ -1,8 +1,10 @@
 package afero
 
 import (
+	"errors"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"time"
 )
@@ -27,6 +29,11 @@
 // on a file outside the base path it returns the given file name and an error,
 // else the given file with the base path prepended
 func (b *BasePathFs) RealPath(name string) (path string, err error) {
+
+	if err := validateBasePathName(name); err != nil {
+		return "", err
+	}
+
 	bpath := filepath.Clean(b.path)
 	path = filepath.Clean(filepath.Join(bpath, name))
 	if !strings.HasPrefix(path, bpath) {
@@ -35,6 +42,22 @@
 	return path, nil
 }
 
+func validateBasePathName(name string) error {
+	if runtime.GOOS != "windows" {
+		// Not much to do here;
+		// the virtual file paths all look absolute on *nix.
+		return nil
+	}
+
+	// On Windows a common mistake would be to provide an absolute OS path
+	// We could strip out the base part, but that would not be very portable.
+	if filepath.IsAbs(name) {
+		return &os.PathError{"realPath", name, errors.New("got a real OS path instead of a virtual")}
+	}
+
+	return nil
+}
+
 func (b *BasePathFs) Chtimes(name string, atime, mtime time.Time) (err error) {
 	if name, err = b.RealPath(name); err != nil {
 		return &os.PathError{"chtimes", name, err}
diff --git a/basepath_test.go b/basepath_test.go
index d2202f9..3c91f5d 100644
--- a/basepath_test.go
+++ b/basepath_test.go
@@ -2,6 +2,8 @@
 
 import (
 	"os"
+	"path/filepath"
+	"runtime"
 	"testing"
 )
 
@@ -35,3 +37,56 @@
 		t.Error(err)
 	}
 }
+
+func TestRealPath(t *testing.T) {
+	fs := NewOsFs()
+	baseDir, err := TempDir(fs, "", "base")
+	if err != nil {
+		t.Fatal("error creating tempDir", err)
+	}
+	defer fs.RemoveAll(baseDir)
+	anotherDir, err := TempDir(fs, "", "another")
+	if err != nil {
+		t.Fatal("error creating tempDir", err)
+	}
+	defer fs.RemoveAll(anotherDir)
+
+	bp := NewBasePathFs(fs, baseDir).(*BasePathFs)
+
+	subDir := filepath.Join(baseDir, "s1")
+
+	realPath, err := bp.RealPath("/s1")
+
+	if err != nil {
+		t.Errorf("Got error %s", err)
+	}
+
+	if realPath != subDir {
+		t.Errorf("Expected \n%s got \n%s", subDir, realPath)
+	}
+
+	if runtime.GOOS == "windows" {
+		_, err = bp.RealPath(anotherDir)
+
+		if err == nil {
+			t.Errorf("Expected error")
+		}
+
+	} else {
+		// on *nix we have no way of just looking at the path and tell that anotherDir
+		// is not inside the base file system.
+		// The user will receive an os.ErrNotExist later.
+		surrealPath, err := bp.RealPath(anotherDir)
+
+		if err != nil {
+			t.Errorf("Got error %s", err)
+		}
+
+		excpected := filepath.Join(baseDir, anotherDir)
+
+		if surrealPath != excpected {
+			t.Errorf("Expected \n%s got \n%s", excpected, surrealPath)
+		}
+	}
+
+}