diff --git a/include/etl/string_stream.h b/include/etl/string_stream.h
index 7842c157..f5ecdef4 100644
--- a/include/etl/string_stream.h
+++ b/include/etl/string_stream.h
@@ -60,7 +60,7 @@ namespace etl
     //*************************************************************************
     /// Construct from text and format spec.
     //*************************************************************************
-    string_stream(etl::istring& text_, etl::format_spec spec_)
+    string_stream(etl::istring& text_, const etl::format_spec& spec_)
       : text(text_)
       , spec(spec_)
     {
@@ -69,7 +69,7 @@ namespace etl
     //*************************************************************************
     /// Set the format spec.
     //*************************************************************************
-    void set_format(etl::format_spec spec_)
+    void set_format(const etl::format_spec& spec_)
     {
       spec = spec_;
     }
@@ -125,7 +125,7 @@ namespace etl
     //*************************************************************************
     /// Stream operators.
     //*************************************************************************
-    friend string_stream& operator <<(string_stream& ss, etl::format_spec spec)
+    friend string_stream& operator <<(string_stream& ss, const etl::format_spec& spec)
     {
       ss.spec = spec;
       return ss;
@@ -174,6 +174,9 @@ namespace etl
 
     etl::istring&    text;
     etl::format_spec spec;
+
+    string_stream(const string_stream&) ETL_DELETE;
+    string_stream& operator =(const string_stream&) ETL_DELETE;
   };
 }
 
diff --git a/include/etl/u16string_stream.h b/include/etl/u16string_stream.h
index f6251ee3..b0055b51 100644
--- a/include/etl/u16string_stream.h
+++ b/include/etl/u16string_stream.h
@@ -60,7 +60,7 @@ namespace etl
     //*************************************************************************
     /// Construct from text and format spec.
     //*************************************************************************
-    u16string_stream(etl::iu16string& text_, etl::u16format_spec spec_)
+    u16string_stream(etl::iu16string& text_, const etl::u16format_spec& spec_)
       : text(text_)
       , spec(spec_)
     {
@@ -69,7 +69,7 @@ namespace etl
     //*************************************************************************
     /// Set the format spec.
     //*************************************************************************
-    void set_format(etl::u16format_spec spec_)
+    void set_format(const etl::u16format_spec& spec_)
     {
       spec = spec_;
     }
@@ -125,7 +125,7 @@ namespace etl
     //*************************************************************************
     /// Stream operators.
     //*************************************************************************
-    friend u16string_stream& operator <<(u16string_stream& ss, etl::u16format_spec spec)
+    friend u16string_stream& operator <<(u16string_stream& ss, const etl::u16format_spec& spec)
     {
       ss.spec = spec;
       return ss;
@@ -174,6 +174,9 @@ namespace etl
 
     etl::iu16string&    text;
     etl::u16format_spec spec;
+
+    u16string_stream(const u16string_stream&) ETL_DELETE;
+    u16string_stream& operator =(const u16string_stream&) ETL_DELETE;
   };
 }
 
diff --git a/include/etl/u32string_stream.h b/include/etl/u32string_stream.h
index 94044744..5f219e93 100644
--- a/include/etl/u32string_stream.h
+++ b/include/etl/u32string_stream.h
@@ -60,7 +60,7 @@ namespace etl
     //*************************************************************************
     /// Construct from text and format spec.
     //*************************************************************************
-    u32string_stream(etl::iu32string& text_, etl::u32format_spec spec_)
+    u32string_stream(etl::iu32string& text_, const etl::u32format_spec& spec_)
       : text(text_)
       , spec(spec_)
     {
@@ -69,7 +69,7 @@ namespace etl
     //*************************************************************************
     /// Set the format spec.
     //*************************************************************************
-    void set_format(etl::u32format_spec spec_)
+    void set_format(const etl::u32format_spec& spec_)
     {
       spec = spec_;
     }
@@ -125,7 +125,7 @@ namespace etl
     //*************************************************************************
     /// Stream operators.
     //*************************************************************************
-    friend u32string_stream& operator <<(u32string_stream& ss, etl::u32format_spec spec)
+    friend u32string_stream& operator <<(u32string_stream& ss, const etl::u32format_spec& spec)
     {
       ss.spec = spec;
       return ss;
@@ -174,6 +174,9 @@ namespace etl
 
     etl::iu32string&    text;
     etl::u32format_spec spec;
+
+    u32string_stream(const u32string_stream&) ETL_DELETE;
+    u32string_stream& operator =(const u32string_stream&) ETL_DELETE;
   };
 }
 
diff --git a/include/etl/wstring_stream.h b/include/etl/wstring_stream.h
index 9c786da6..e72a9c21 100644
--- a/include/etl/wstring_stream.h
+++ b/include/etl/wstring_stream.h
@@ -60,7 +60,7 @@ namespace etl
     //*************************************************************************
     /// Construct from text and format spec.
     //*************************************************************************
-    wstring_stream(etl::iwstring& text_, etl::wformat_spec spec_)
+    wstring_stream(etl::iwstring& text_, const etl::wformat_spec& spec_)
       : text(text_)
       , spec(spec_)
     {
@@ -69,7 +69,7 @@ namespace etl
     //*************************************************************************
     /// Set the format spec.
     //*************************************************************************
-    void set_format(etl::wformat_spec spec_)
+    void set_format(const etl::wformat_spec& spec_)
     {
       spec = spec_;
     }
@@ -125,7 +125,7 @@ namespace etl
     //*************************************************************************
     /// Stream operators.
     //*************************************************************************
-    friend wstring_stream& operator <<(wstring_stream& ss, etl::wformat_spec spec)
+    friend wstring_stream& operator <<(wstring_stream& ss, const etl::wformat_spec& spec)
     {
       ss.spec = spec;
       return ss;
@@ -174,6 +174,9 @@ namespace etl
 
     etl::iwstring&    text;
     etl::wformat_spec spec;
+
+    wstring_stream(const wstring_stream&) ETL_DELETE;
+    wstring_stream& operator =(const wstring_stream&) ETL_DELETE;
   };
 }