diff --git a/Objects/stringlib/asciilib.h b/Objects/stringlib/asciilib.h
index 935a9c7..bfd5d75a 100644
--- a/Objects/stringlib/asciilib.h
+++ b/Objects/stringlib/asciilib.h
@@ -6,6 +6,7 @@
 #define FASTSEARCH               asciilib_fastsearch
 #define STRINGLIB(F)             asciilib_##F
 #define STRINGLIB_OBJECT         PyUnicodeObject
+#define STRINGLIB_SIZEOF_CHAR    1
 #define STRINGLIB_CHAR           Py_UCS1
 #define STRINGLIB_TYPE_NAME      "unicode"
 #define STRINGLIB_PARSE_CODE     "U"
diff --git a/Objects/stringlib/fastsearch.h b/Objects/stringlib/fastsearch.h
index 33ab6ff..085ec6a 100644
--- a/Objects/stringlib/fastsearch.h
+++ b/Objects/stringlib/fastsearch.h
@@ -115,11 +115,17 @@
             unsigned char needle;
             int use_needle = 1;
             needle = p[0] & 0xff;
-            if (needle == 0 && sizeof(STRINGLIB_CHAR) > 1) {
+#if STRINGLIB_SIZEOF_CHAR > 1
+            if (needle == 0) {
                 needle = (p[0] >> 8) & 0xff;
-                if (needle >= 32)
+#if STRINGLIB_SIZEOF_CHAR > 2
+                if (needle == 0)
+                    needle = (p[0] >> 16) & 0xff;
+#endif
+                if (needle >= 32 || needle == 0)
                     use_needle = 0;
             }
+#endif
             if (use_needle)
                 return STRINGLIB(fastsearch_memchr_1char)
                        (s, n, p[0], needle, maxcount, mode);
diff --git a/Objects/stringlib/stringdefs.h b/Objects/stringlib/stringdefs.h
index 9619332..41449fc 100644
--- a/Objects/stringlib/stringdefs.h
+++ b/Objects/stringlib/stringdefs.h
@@ -9,6 +9,7 @@
 #define FASTSEARCH fastsearch
 #define STRINGLIB(F) stringlib_##F
 #define STRINGLIB_OBJECT         PyBytesObject
+#define STRINGLIB_SIZEOF_CHAR    1
 #define STRINGLIB_CHAR           char
 #define STRINGLIB_TYPE_NAME      "string"
 #define STRINGLIB_PARSE_CODE     "S"
diff --git a/Objects/stringlib/ucs1lib.h b/Objects/stringlib/ucs1lib.h
index c0f7adf..0b82a84 100644
--- a/Objects/stringlib/ucs1lib.h
+++ b/Objects/stringlib/ucs1lib.h
@@ -6,6 +6,7 @@
 #define FASTSEARCH               ucs1lib_fastsearch
 #define STRINGLIB(F)             ucs1lib_##F
 #define STRINGLIB_OBJECT         PyUnicodeObject
+#define STRINGLIB_SIZEOF_CHAR    1
 #define STRINGLIB_CHAR           Py_UCS1
 #define STRINGLIB_TYPE_NAME      "unicode"
 #define STRINGLIB_PARSE_CODE     "U"
diff --git a/Objects/stringlib/ucs2lib.h b/Objects/stringlib/ucs2lib.h
index fc62fb7..18117ef 100644
--- a/Objects/stringlib/ucs2lib.h
+++ b/Objects/stringlib/ucs2lib.h
@@ -6,6 +6,7 @@
 #define FASTSEARCH               ucs2lib_fastsearch
 #define STRINGLIB(F)             ucs2lib_##F
 #define STRINGLIB_OBJECT         PyUnicodeObject
+#define STRINGLIB_SIZEOF_CHAR    2
 #define STRINGLIB_CHAR           Py_UCS2
 #define STRINGLIB_TYPE_NAME      "unicode"
 #define STRINGLIB_PARSE_CODE     "U"
diff --git a/Objects/stringlib/ucs4lib.h b/Objects/stringlib/ucs4lib.h
index be1206a..988ddc0 100644
--- a/Objects/stringlib/ucs4lib.h
+++ b/Objects/stringlib/ucs4lib.h
@@ -6,6 +6,7 @@
 #define FASTSEARCH               ucs4lib_fastsearch
 #define STRINGLIB(F)             ucs4lib_##F
 #define STRINGLIB_OBJECT         PyUnicodeObject
+#define STRINGLIB_SIZEOF_CHAR    4
 #define STRINGLIB_CHAR           Py_UCS4
 #define STRINGLIB_TYPE_NAME      "unicode"
 #define STRINGLIB_PARSE_CODE     "U"
diff --git a/Objects/stringlib/undef.h b/Objects/stringlib/undef.h
index 40b4391..fd87e56 100644
--- a/Objects/stringlib/undef.h
+++ b/Objects/stringlib/undef.h
@@ -1,5 +1,6 @@
 #undef  FASTSEARCH
 #undef  STRINGLIB
+#undef  STRINGLIB_SIZEOF_CHAR
 #undef  STRINGLIB_CHAR
 #undef  STRINGLIB_STR
 #undef  STRINGLIB_LEN
diff --git a/Objects/stringlib/unicodedefs.h b/Objects/stringlib/unicodedefs.h
index 0c40b80..5c0761a 100644
--- a/Objects/stringlib/unicodedefs.h
+++ b/Objects/stringlib/unicodedefs.h
@@ -9,6 +9,7 @@
 #define FASTSEARCH               fastsearch
 #define STRINGLIB(F)             stringlib_##F
 #define STRINGLIB_OBJECT         PyUnicodeObject
+#define STRINGLIB_SIZEOF_CHAR    Py_UNICODE_SIZE
 #define STRINGLIB_CHAR           Py_UNICODE
 #define STRINGLIB_TYPE_NAME      "unicode"
 #define STRINGLIB_PARSE_CODE     "U"