diff --git a/paths.go b/paths.go
index b969606..a9e752b 100644
--- a/paths.go
+++ b/paths.go
@@ -188,12 +188,17 @@ func (p *Path) Clean() *Path {
 
 // IsInsideDir returns true if the current path is inside the provided
 // dir
-func (p *Path) IsInsideDir(dir *Path) (bool, error) {
+func (p *Path) IsInsideDir(dir *Path) bool {
 	rel, err := filepath.Rel(dir.path, p.path)
 	if err != nil {
-		return false, err
+		// If the dir cannot be made relative to this path it means
+		// that it belong to a different filesystems, so it cannot be
+		// inside this path.
+		return false
 	}
-	return !strings.Contains(rel, ".."+string(os.PathSeparator)) && rel != ".." && rel != ".", nil
+	return !strings.Contains(rel, ".."+string(os.PathSeparator)) &&
+		rel != ".." &&
+		rel != "."
 }
 
 // Parent returns all but the last element of path, typically the path's
diff --git a/paths_test.go b/paths_test.go
index 4e7817a..fba0481 100644
--- a/paths_test.go
+++ b/paths_test.go
@@ -154,16 +154,13 @@ func TestResetStatCacheWhenFollowingSymlink(t *testing.T) {
 }
 
 func TestIsInsideDir(t *testing.T) {
-	inside := func(a, b *Path) {
-		in, err := a.IsInsideDir(b)
-		require.NoError(t, err)
-		require.True(t, in, "%s is inside %s", a, b)
+	notInside := func(a, b *Path) {
+		require.False(t, a.IsInsideDir(b), "%s is inside %s", a, b)
 	}
 
-	notInside := func(a, b *Path) {
-		in, err := a.IsInsideDir(b)
-		require.NoError(t, err)
-		require.False(t, in, "%s is inside %s", a, b)
+	inside := func(a, b *Path) {
+		require.True(t, a.IsInsideDir(b), "%s is inside %s", a, b)
+		notInside(b, a)
 	}
 
 	f1 := New("/a/b/c")
@@ -196,6 +193,14 @@ func TestIsInsideDir(t *testing.T) {
 	f5 := New("/home/megabug/a15/packages")
 	notInside(f5, f4)
 	notInside(f4, f5)
+
+	if runtime.GOOS == "windows" {
+		f6 := New("C:\\", "A")
+		f7 := New("C:\\", "A", "B", "C")
+		f8 := New("E:\\", "A", "B", "C")
+		inside(f7, f6)
+		notInside(f8, f6)
+	}
 }
 
 func TestReadFileAsLines(t *testing.T) {
@@ -372,9 +377,7 @@ func TestWriteToTempFile(t *testing.T) {
 	defer tmp.Remove()
 	require.NoError(t, err)
 	require.True(t, strings.HasPrefix(tmp.Base(), "prefix"))
-	inside, err := tmp.IsInsideDir(tmpDir)
-	require.NoError(t, err)
-	require.True(t, inside)
+	require.True(t, tmp.IsInsideDir(tmpDir))
 	data, err := tmp.ReadFile()
 	require.NoError(t, err)
 	require.Equal(t, tmpData, data)