diff --git a/eeschema/netlist_exporters/netlist_exporter_spice.cpp b/eeschema/netlist_exporters/netlist_exporter_spice.cpp
index 2f4217631d..87698e9514 100644
--- a/eeschema/netlist_exporters/netlist_exporter_spice.cpp
+++ b/eeschema/netlist_exporters/netlist_exporter_spice.cpp
@@ -180,7 +180,7 @@ void NETLIST_EXPORTER_SPICE::ReadDirectives()
             else
                 continue;
 
-            tao::pegtl::string_input<> in( text.ToStdString() + "\n", "from_content" );
+            tao::pegtl::string_input<> in( ( text + "\n" ).ToUTF8(), "from_content" );
             std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
             try
@@ -320,8 +320,8 @@ bool NETLIST_EXPORTER_SPICE::readModel( SCH_SYMBOL& aSymbol, SPICE_ITEM& aItem )
         catch( const IO_ERROR& e )
         {
             DisplayErrorMessage( nullptr,
-                wxString::Format( "Failed reading %s simulation model.", aItem.refName ),
-                e.What() );
+                    wxString::Format( _( "Failed reading %s simulation model." ), aItem.refName ),
+                    e.What() );
             return false;
         }
     }
diff --git a/eeschema/sim/sim_model.cpp b/eeschema/sim/sim_model.cpp
index 7f1eb5c46e..7024470f41 100644
--- a/eeschema/sim/sim_model.cpp
+++ b/eeschema/sim/sim_model.cpp
@@ -380,9 +380,9 @@ SIM_MODEL::SPICE_INFO SIM_MODEL::SpiceInfo( TYPE aType )
 }
 
 
-TYPE SIM_MODEL::ReadTypeFromSpiceCode( const std::string& aSpiceCode )
+TYPE SIM_MODEL::ReadTypeFromSpiceCode( const wxString& aSpiceCode )
 {
-    tao::pegtl::string_input<> in( aSpiceCode, "Spice_Code" );
+    tao::pegtl::string_input<> in( aSpiceCode.ToUTF8(), "Spice_Code" );
     std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
     try
@@ -584,7 +584,7 @@ TYPE SIM_MODEL::InferTypeFromRefAndValue( const wxString& aRef, const wxString&
     case TYPE::TLINE_Z0:
         try
         {
-            tao::pegtl::string_input<> in( aValue.ToStdString(), "Value" );
+            tao::pegtl::string_input<> in( aValue.ToUTF8(), "Value" );
             auto root = tao::pegtl::parse_tree::parse<
                 SIM_MODEL_PARSER::fieldParamValuePairsGrammar,
                 SIM_MODEL_PARSER::fieldParamValuePairsSelector>
@@ -700,7 +700,7 @@ std::unique_ptr<SIM_MODEL> SIM_MODEL::Create( TYPE aType, unsigned aSymbolPinCou
 }
 
 
-std::unique_ptr<SIM_MODEL> SIM_MODEL::Create( const std::string& aSpiceCode )
+std::unique_ptr<SIM_MODEL> SIM_MODEL::Create( const wxString& aSpiceCode )
 {
     std::unique_ptr<SIM_MODEL> model = create( ReadTypeFromSpiceCode( aSpiceCode ) );
 
@@ -837,12 +837,12 @@ void SIM_MODEL::SetFieldValue( std::vector<T>& aFields, const wxString& aFieldNa
 }
 
 
-void SIM_MODEL::ReadSpiceCode( const std::string& aSpiceCode )
+void SIM_MODEL::ReadSpiceCode( const wxString& aSpiceCode )
 {
     // The default behavior is to treat the Spice param=value pairs as the model parameters and
     // values (for many models the correspondence is not exact, so this function is overridden).
 
-    tao::pegtl::string_input<> in( aSpiceCode, "Spice_Code" );
+    tao::pegtl::string_input<> in( aSpiceCode.ToUTF8(), "Spice_Code" );
     std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
     try
@@ -1260,7 +1260,7 @@ void SIM_MODEL::ParseParamsField( const wxString& aParamsField )
 {
     LOCALE_IO toggle;
 
-    tao::pegtl::string_input<> in( aParamsField.ToStdString(), "Sim_Params" );
+    tao::pegtl::string_input<> in( aParamsField.ToUTF8(), "Sim_Params" );
     std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
     try
@@ -1329,7 +1329,7 @@ void SIM_MODEL::ParsePinsField( unsigned aSymbolPinCount, const wxString& aPinsF
 
     LOCALE_IO toggle;
 
-    tao::pegtl::string_input<> in( aPinsField.ToStdString(), PINS_FIELD );
+    tao::pegtl::string_input<> in( aPinsField.ToUTF8(), PINS_FIELD );
     std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
     try
diff --git a/eeschema/sim/sim_model.h b/eeschema/sim/sim_model.h
index b481ace6e0..581534b3c8 100644
--- a/eeschema/sim/sim_model.h
+++ b/eeschema/sim/sim_model.h
@@ -373,7 +373,7 @@ public:
                   DIR aDir = DIR_INOUT,
                   SIM_VALUE::TYPE aType = SIM_VALUE::TYPE_FLOAT,
                   FLAGS aFlags = {},
-                  std::string aUnit = "",
+                  const wxString& aUnit = "",
                   CATEGORY aCategory = CATEGORY::PRINCIPAL,
                   const wxString& aDefaultValue = "",
                   const wxString& aDefaultValueOfOtherVariant = "",
@@ -415,7 +415,7 @@ public:
     static SPICE_INFO SpiceInfo( TYPE aType );
 
 
-    static TYPE ReadTypeFromSpiceCode( const std::string& aSpiceCode );
+    static TYPE ReadTypeFromSpiceCode( const wxString& aSpiceCode );
 
     template <typename T>
     static TYPE ReadTypeFromFields( const std::vector<T>& aFields );
@@ -427,7 +427,7 @@ public:
 
 
     static std::unique_ptr<SIM_MODEL> Create( TYPE aType, unsigned aSymbolPinCount = 0 );
-    static std::unique_ptr<SIM_MODEL> Create( const std::string& aSpiceCode );
+    static std::unique_ptr<SIM_MODEL> Create( const wxString& aSpiceCode );
     static std::unique_ptr<SIM_MODEL> Create( const SIM_MODEL& aBaseModel,
                                               unsigned         aSymbolPinCount );
 
@@ -456,7 +456,7 @@ public:
     SIM_MODEL& operator=(SIM_MODEL&& aOther ) = delete;
 
 
-    virtual void ReadSpiceCode( const std::string& aSpiceCode );
+    virtual void ReadSpiceCode( const wxString& aSpiceCode );
 
     template <typename T>
     void ReadDataFields( unsigned aSymbolPinCount, const std::vector<T>* aFields );
diff --git a/eeschema/sim/sim_model_ideal.cpp b/eeschema/sim/sim_model_ideal.cpp
index 94bfb79686..783f2444b0 100644
--- a/eeschema/sim/sim_model_ideal.cpp
+++ b/eeschema/sim/sim_model_ideal.cpp
@@ -127,7 +127,7 @@ void SIM_MODEL_IDEAL::inferredReadDataFields( unsigned aSymbolPinCount, const st
         {
             wxString value = GetFieldValue( aFields, VALUE_FIELD );
 
-            tao::pegtl::string_input<> in( value.ToStdString(), "Value" );
+            tao::pegtl::string_input<> in( value.ToUTF8(), "Value" );
             auto root = tao::pegtl::parse_tree::parse<
                 SIM_MODEL_PARSER::fieldFloatValueGrammar,
                 SIM_MODEL_PARSER::fieldFloatValueSelector>
diff --git a/eeschema/sim/sim_model_source.cpp b/eeschema/sim/sim_model_source.cpp
index b9437af42f..69423f8244 100644
--- a/eeschema/sim/sim_model_source.cpp
+++ b/eeschema/sim/sim_model_source.cpp
@@ -113,7 +113,7 @@ wxString SIM_MODEL_SOURCE::GenerateSpiceItemLine( const wxString& aRefName,
         case TYPE::V_PWL:
         case TYPE::I_PWL:
         {
-            tao::pegtl::string_input<> in( GetParam( 0 ).value->ToString().ToStdString(),
+            tao::pegtl::string_input<> in( GetParam( 0 ).value->ToString().ToUTF8(),
                                            "from_content" );
             std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
diff --git a/eeschema/sim/sim_model_subckt.cpp b/eeschema/sim/sim_model_subckt.cpp
index 232f57da62..001e1df5bd 100644
--- a/eeschema/sim/sim_model_subckt.cpp
+++ b/eeschema/sim/sim_model_subckt.cpp
@@ -52,9 +52,9 @@ SIM_MODEL_SUBCKT::SIM_MODEL_SUBCKT( TYPE aType )
 }
 
 
-void SIM_MODEL_SUBCKT::ReadSpiceCode( const std::string& aSpiceCode )
+void SIM_MODEL_SUBCKT::ReadSpiceCode( const wxString& aSpiceCode )
 {
-    tao::pegtl::string_input<> in( aSpiceCode, "from_content" );
+    tao::pegtl::string_input<> in( aSpiceCode.ToUTF8(), "from_content" );
     std::unique_ptr<tao::pegtl::parse_tree::node> root;
 
     try
diff --git a/eeschema/sim/sim_model_subckt.h b/eeschema/sim/sim_model_subckt.h
index bd9e0ad653..77444fc851 100644
--- a/eeschema/sim/sim_model_subckt.h
+++ b/eeschema/sim/sim_model_subckt.h
@@ -33,7 +33,7 @@ class SIM_MODEL_SUBCKT : public SIM_MODEL
 public:
     SIM_MODEL_SUBCKT( TYPE aType );
 
-    void ReadSpiceCode( const std::string& aSpiceCode ) override;
+    void ReadSpiceCode( const wxString& aSpiceCode ) override;
     wxString GenerateSpiceModelLine( const wxString& aModelName ) const override;
     std::vector<wxString> GenerateSpiceCurrentNames( const wxString& aRefName ) const override;
     void SetBaseModel( const SIM_MODEL& aBaseModel ) override;
diff --git a/eeschema/sim/sim_value.cpp b/eeschema/sim/sim_value.cpp
index 72c3298bc3..e9e6d36fd2 100644
--- a/eeschema/sim/sim_value.cpp
+++ b/eeschema/sim/sim_value.cpp
@@ -128,7 +128,7 @@ bool SIM_VALUE_GRAMMAR::IsValid( const wxString& aString,
                                 SIM_VALUE::TYPE aValueType,
                                 NOTATION aNotation )
 {
-    tao::pegtl::string_input<> in( aString.ToStdString(), "from_content" );
+    tao::pegtl::string_input<> in( aString.ToUTF8(), "from_content" );
 
     try
     {
@@ -192,7 +192,7 @@ SIM_VALUE_PARSER::PARSE_RESULT SIM_VALUE_PARSER::Parse( const wxString& aString,
 {
     LOCALE_IO toggle;
 
-    tao::pegtl::string_input<> in( aString.ToStdString(), "from_content" );
+    tao::pegtl::string_input<> in( aString.ToUTF8(), "from_content" );
     std::unique_ptr<tao::pegtl::parse_tree::node> root;
     PARSE_RESULT result;