diff --git a/src/Text.cc b/src/Text.cc
index c68a851e..1876aef0 100644
--- a/src/Text.cc
+++ b/src/Text.cc
@@ -257,16 +257,17 @@ std::string TextTranscoderUTF8ToCustomSJIS::on_untranslatable(const void** src,
   }
 }
 
-TextTranscoder tt_8859_to_utf8("UTF-8", "ISO-8859-1");
-TextTranscoder tt_utf8_to_8859("ISO-8859-1", "UTF-8");
-TextTranscoder tt_standard_sjis_to_utf8("UTF-8", "SHIFT_JIS");
-TextTranscoder tt_utf8_to_standard_sjis("SHIFT_JIS", "UTF-8");
-TextTranscoderCustomSJISToUTF8 tt_sega_sjis_to_utf8;
-TextTranscoderUTF8ToCustomSJIS tt_utf8_to_sega_sjis;
-TextTranscoder tt_utf16_to_utf8("UTF-8", "UTF-16LE");
-TextTranscoder tt_utf8_to_utf16("UTF-16LE", "UTF-8");
-TextTranscoder tt_ascii_to_utf8("UTF-8", "ASCII");
-TextTranscoder tt_utf8_to_ascii("ASCII", "UTF-8");
+// iconv_t is not thread-safe, so we need a separate one of these for each thread
+thread_local TextTranscoder tt_8859_to_utf8("UTF-8", "ISO-8859-1");
+thread_local TextTranscoder tt_utf8_to_8859("ISO-8859-1", "UTF-8");
+thread_local TextTranscoder tt_standard_sjis_to_utf8("UTF-8", "SHIFT_JIS");
+thread_local TextTranscoder tt_utf8_to_standard_sjis("SHIFT_JIS", "UTF-8");
+thread_local TextTranscoderCustomSJISToUTF8 tt_sega_sjis_to_utf8;
+thread_local TextTranscoderUTF8ToCustomSJIS tt_utf8_to_sega_sjis;
+thread_local TextTranscoder tt_utf16_to_utf8("UTF-8", "UTF-16LE");
+thread_local TextTranscoder tt_utf8_to_utf16("UTF-16LE", "UTF-8");
+thread_local TextTranscoder tt_ascii_to_utf8("UTF-8", "ASCII");
+thread_local TextTranscoder tt_utf8_to_ascii("ASCII", "UTF-8");
 
 std::string tt_encode_marked_optional(const std::string& utf8, Language default_language, bool is_utf16) {
   if (is_utf16) {
diff --git a/src/Text.hh b/src/Text.hh
index a9707805..52024f67 100644
--- a/src/Text.hh
+++ b/src/Text.hh
@@ -77,16 +77,16 @@ protected:
   virtual std::string on_untranslatable(const void** src, size_t* size) const;
 };
 
-extern TextTranscoder tt_8859_to_utf8;
-extern TextTranscoder tt_utf8_to_8859;
-extern TextTranscoder tt_standard_sjis_to_utf8;
-extern TextTranscoder tt_utf8_to_standard_sjis;
-extern TextTranscoderCustomSJISToUTF8 tt_sega_sjis_to_utf8;
-extern TextTranscoderUTF8ToCustomSJIS tt_utf8_to_sega_sjis;
-extern TextTranscoder tt_utf16_to_utf8;
-extern TextTranscoder tt_utf8_to_utf16;
-extern TextTranscoder tt_ascii_to_utf8;
-extern TextTranscoder tt_utf8_to_ascii;
+extern thread_local TextTranscoder tt_8859_to_utf8;
+extern thread_local TextTranscoder tt_utf8_to_8859;
+extern thread_local TextTranscoder tt_standard_sjis_to_utf8;
+extern thread_local TextTranscoder tt_utf8_to_standard_sjis;
+extern thread_local TextTranscoderCustomSJISToUTF8 tt_sega_sjis_to_utf8;
+extern thread_local TextTranscoderUTF8ToCustomSJIS tt_utf8_to_sega_sjis;
+extern thread_local TextTranscoder tt_utf16_to_utf8;
+extern thread_local TextTranscoder tt_utf8_to_utf16;
+extern thread_local TextTranscoder tt_ascii_to_utf8;
+extern thread_local TextTranscoder tt_utf8_to_ascii;
 
 std::string tt_encode_marked_optional(const std::string& utf8, Language default_language, bool is_utf16);
 std::string tt_encode_marked(const std::string& utf8, Language default_language, bool is_utf16);