diff --git a/css/css.go b/css/css.go
index a0261a03c0..580b848c40 100644
--- a/css/css.go
+++ b/css/css.go
@@ -135,6 +135,10 @@ func (t Token) IsLengthPercentage() bool {
 
 // Minify minifies CSS data, it reads from r and writes to w.
 func (o *Minifier) Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
+	tmp := &Minifier{}
+	*tmp = *o
+	o = tmp
+
 	o.newPrecision = o.Precision
 	if o.newPrecision <= 0 || 15 < o.newPrecision {
 		o.newPrecision = 15 // minimum number of digits a double can represent exactly
diff --git a/html/html.go b/html/html.go
index 345f579fb7..23cd2ca075 100644
--- a/html/html.go
+++ b/html/html.go
@@ -75,6 +75,7 @@ func (o *Minifier) Minify(m *minify.M, w io.Writer, r io.Reader, _ map[string]st
 	if o.KeepConditionalComments {
 		fmt.Println("DEPRECATED: KeepConditionalComments is replaced by KeepSpecialComments")
 		o.KeepSpecialComments = true
+		o.KeepConditionalComments = false // omit next warning
 	}
 
 	omitSpace := true // if true the next leading space is omitted
diff --git a/svg/svg.go b/svg/svg.go
index 22ac1bc852..f86107b77f 100644
--- a/svg/svg.go
+++ b/svg/svg.go
@@ -41,6 +41,10 @@ func Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) err
 
 // Minify minifies SVG data, it reads from r and writes to w.
 func (o *Minifier) Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
+	tmp := &Minifier{}
+	*tmp = *o
+	o = tmp
+
 	o.newPrecision = o.Precision
 	if o.newPrecision <= 0 || 15 < o.newPrecision {
 		o.newPrecision = 15 // minimum number of digits a double can represent exactly