diff --git a/src/Lexer.cpp b/src/Lexer.cpp
index d8d52bbd4..a6435fe89 100644
--- a/src/Lexer.cpp
+++ b/src/Lexer.cpp
@@ -24,12 +24,14 @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <cmake.h>
 #include <ctype.h>
 #include <utf8.h>
 #include <ISO8601.h>
 #include <Date.h>
 #include <Duration.h>
 #include <Lexer.h>
+#include <i18n.h>
 
 std::string Lexer::dateFormat = "";
 
@@ -175,7 +177,7 @@ bool Lexer::token (std::string& result, Type& type)
         shift ();
       }
       else
-        throw std::string ("Unexpected error 1");
+        throw std::string (STRING_LEX_IMMEDIATE_UNK);
       break;
 
     case typeString:
@@ -384,7 +386,7 @@ bool Lexer::token (std::string& result, Type& type)
       break;
 
     default:
-      throw std::string ("Unexpected error 2");
+      throw std::string (STRING_LEX_TYPE_UNK);
       break;
     }
 
@@ -511,7 +513,7 @@ bool Lexer::word (std::string& token, Type& type)
       break;
 
     default:
-      throw std::string ("Unexpected error 2");
+      throw std::string (STRING_LEX_TYPE_UNK);
       break;
     }
 
@@ -530,6 +532,7 @@ void Lexer::ambiguity (bool value)
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// No L10N - these are for internal purposes.
 const std::string Lexer::type_name (const Type& type)
 {
   switch (type)
diff --git a/src/eng-USA.h b/src/eng-USA.h
index 972b0c08f..83b8989d0 100644
--- a/src/eng-USA.h
+++ b/src/eng-USA.h
@@ -175,6 +175,13 @@
 #define STRING_VARIANT_SQRT_NEG      "Cannot take the square root of a negative number."
 #define STRING_VARIANT_COERCE_UNK    "Cannot coerce data either to or from an unknown type"
 
+// Lexer
+//
+// These are errors generated at the lowest level of input analysis,
+// at the character level.
+#define STRING_LEX_IMMEDIATE_UNK     "Lexer start failure, unknown characters found immediately."
+#define STRING_LEX_TYPE_UNK          "Lexer cannot process and unknown token type."
+
 // A3
 #define STRING_A3_OVERRIDE_PROBLEM   "Problem with override: {1}"
 #define STRING_A3_MISMATCHED_PARENS  "Mismatched parentheses in expression"
diff --git a/src/esp-ESP.h b/src/esp-ESP.h
index f57a84025..ecc8e33f2 100644
--- a/src/esp-ESP.h
+++ b/src/esp-ESP.h
@@ -175,6 +175,13 @@
 #define STRING_VARIANT_SQRT_NEG      "Cannot take the square root of a negative number."
 #define STRING_VARIANT_COERCE_UNK    "Cannot coerce data either to or from an unknown type"
 
+// Lexer
+//
+// These are errors generated at the lowest level of input analysis,
+// at the character level.
+#define STRING_LEX_IMMEDIATE_UNK     "Lexer start failure, unknown characters found immediately."
+#define STRING_LEX_TYPE_UNK          "Lexer cannot process and unknown token type."
+
 // A3
 // Sobrescritura: de R.A.E. sobrescribir
 #define STRING_A3_OVERRIDE_PROBLEM   "Problema con sobrescritura: {1}"
diff --git a/src/fra-FRA.h b/src/fra-FRA.h
index 8f0ddb61c..0bace277a 100644
--- a/src/fra-FRA.h
+++ b/src/fra-FRA.h
@@ -175,6 +175,13 @@
 #define STRING_VARIANT_SQRT_NEG      "Cannot take the square root of a negative number."
 #define STRING_VARIANT_COERCE_UNK    "Cannot coerce data either to or from an unknown type"
 
+// Lexer
+//
+// These are errors generated at the lowest level of input analysis,
+// at the character level.
+#define STRING_LEX_IMMEDIATE_UNK     "Lexer start failure, unknown characters found immediately."
+#define STRING_LEX_TYPE_UNK          "Lexer cannot process and unknown token type."
+
 // A3
 #define STRING_A3_OVERRIDE_PROBLEM   "Problème avec l'écrasement de {1}"
 #define STRING_A3_MISMATCHED_PARENS  "Parenthèses incohérentes dans l'expression"
diff --git a/src/ita-ITA.h b/src/ita-ITA.h
index 179365945..9cd64e3fb 100644
--- a/src/ita-ITA.h
+++ b/src/ita-ITA.h
@@ -176,6 +176,13 @@
 #define STRING_VARIANT_SQRT_NEG      "Cannot take the square root of a negative number."
 #define STRING_VARIANT_COERCE_UNK    "Cannot coerce data either to or from an unknown type"
 
+// Lexer
+//
+// These are errors generated at the lowest level of input analysis,
+// at the character level.
+#define STRING_LEX_IMMEDIATE_UNK     "Lexer start failure, unknown characters found immediately."
+#define STRING_LEX_TYPE_UNK          "Lexer cannot process and unknown token type."
+
 // A3
 #define STRING_A3_OVERRIDE_PROBLEM   "Problema di modifica: {1}"
 #define STRING_A3_MISMATCHED_PARENS  "Mancata corrispondenza nell'uso delle parentesi nell'espressione"
diff --git a/src/por-PRT.h b/src/por-PRT.h
index 005a1ffdf..51e47f0fc 100644
--- a/src/por-PRT.h
+++ b/src/por-PRT.h
@@ -175,6 +175,13 @@
 #define STRING_VARIANT_SQRT_NEG      "Cannot take the square root of a negative number."
 #define STRING_VARIANT_COERCE_UNK    "Cannot coerce data either to or from an unknown type"
 
+// Lexer
+//
+// These are errors generated at the lowest level of input analysis,
+// at the character level.
+#define STRING_LEX_IMMEDIATE_UNK     "Lexer start failure, unknown characters found immediately."
+#define STRING_LEX_TYPE_UNK          "Lexer cannot process and unknown token type."
+
 // A3
 #define STRING_A3_OVERRIDE_PROBLEM   "Problema com a alteração: {1}"
 #define STRING_A3_MISMATCHED_PARENS  "Erro de não correspondência de parentesis na expressão"