diff --git a/headers/private/libroot/locale/ICUCtypeData.h b/headers/private/libroot/locale/ICUCtypeData.h
index 38d91f2973..b560205a7a 100644
--- a/headers/private/libroot/locale/ICUCtypeData.h
+++ b/headers/private/libroot/locale/ICUCtypeData.h
@@ -32,9 +32,14 @@ public:
 			const char*			GetLanginfo(int index);
 
 private:
-			unsigned short		fClassInfo[256];
-			int					fToLowerMap[256];
-			int					fToUpperMap[256];
+			/*
+			 * the following arrays have 257 elements where the first is a
+			 * dummy element (containing the neutral/identity value) used when
+			 * the array is accessed as in 'isblank(EOF)' (i.e. with index -1).
+			 */
+			unsigned short		fClassInfo[257];
+			int					fToLowerMap[257];
+			int					fToUpperMap[257];
 
 			LocaleCtypeDataBridge*	fDataBridge;
 };
diff --git a/headers/private/libroot/locale/PosixCtype.h b/headers/private/libroot/locale/PosixCtype.h
index 9dfa51e83c..cf99c92672 100644
--- a/headers/private/libroot/locale/PosixCtype.h
+++ b/headers/private/libroot/locale/PosixCtype.h
@@ -9,9 +9,14 @@
 namespace BPrivate {
 
 
-extern const unsigned short gPosixClassInfo[256];
-extern const int gPosixToLowerMap[256];
-extern const int gPosixToUpperMap[256];
+/*
+ * the following arrays have 257 elements where the first is a
+ * dummy element (containing the neutral/identity value) used when
+ * the array is accessed as in 'isblank(EOF)' (i.e. with index -1).
+ */
+extern const unsigned short gPosixClassInfo[257];
+extern const int gPosixToLowerMap[257];
+extern const int gPosixToUpperMap[257];
 
 
 }	// namespace BPrivate
diff --git a/src/system/libroot/add-ons/icu/locale/ICUCtypeData.cpp b/src/system/libroot/add-ons/icu/locale/ICUCtypeData.cpp
index 432ef1e15a..f477ca9ee3 100644
--- a/src/system/libroot/add-ons/icu/locale/ICUCtypeData.cpp
+++ b/src/system/libroot/add-ons/icu/locale/ICUCtypeData.cpp
@@ -30,9 +30,9 @@ ICUCtypeData::~ICUCtypeData()
 void
 ICUCtypeData::Initialize(LocaleCtypeDataBridge* dataBridge)
 {
-	*dataBridge->addrOfClassInfoTable = fClassInfo;
-	*dataBridge->addrOfToLowerTable = fToLowerMap;
-	*dataBridge->addrOfToUpperTable = fToUpperMap;
+	*dataBridge->addrOfClassInfoTable = &fClassInfo[1];
+	*dataBridge->addrOfToLowerTable = &fToLowerMap[1];
+	*dataBridge->addrOfToUpperTable = &fToUpperMap[1];
 	fDataBridge = dataBridge;
 }
 
@@ -97,9 +97,9 @@ ICUCtypeData::SetTo(const Locale& locale, const char* posixLocaleName)
 			if (U_SUCCESS(icuStatus))
 				toUpper = (unsigned char)buffer[0];
 		}
-		fClassInfo[i] = classInfo;
-		fToLowerMap[i] = toLower;
-		fToUpperMap[i] = toUpper;
+		fClassInfo[i + 1] = classInfo;
+		fToLowerMap[i + 1] = toLower;
+		fToUpperMap[i + 1] = toUpper;
 	}
 
 	return B_OK;
@@ -124,6 +124,9 @@ ICUCtypeData::SetToPosix()
 int
 ICUCtypeData::IsWCType(wint_t wc, wctype_t charClass)
 {
+	if (wc == WEOF)
+		return 0;
+
 	switch (charClass) {
 		case _ISalnum:
 			return u_hasBinaryProperty(wc, UCHAR_POSIX_ALNUM);
diff --git a/src/system/libroot/posix/locale/LocaleData.cpp b/src/system/libroot/posix/locale/LocaleData.cpp
index a17ff232ed..ae5de96ef1 100644
--- a/src/system/libroot/posix/locale/LocaleData.cpp
+++ b/src/system/libroot/posix/locale/LocaleData.cpp
@@ -27,7 +27,13 @@
 namespace BPrivate {
 
 
-const unsigned short gPosixClassInfo[256] = {
+/*
+ * the following arrays have 257 elements where the first is a
+ * dummy element (containing the neutral/identity value) used when
+ * the array is accessed as in 'isblank(EOF)' (i.e. with index -1).
+ */
+const unsigned short gPosixClassInfo[257] = {
+	/*  -1 */   0,	// neutral value
 	/*   0 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
 	/*   8 */	_IScntrl, _ISblank|_IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl, _IScntrl,
 	/*  16 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
@@ -62,7 +68,8 @@ const unsigned short gPosixClassInfo[256] = {
 	/* 248 */	0, 0, 0, 0, 0, 0, 0, 0
 };
 
-const int gPosixToLowerMap[256] = {
+const int gPosixToLowerMap[257] = {
+	/*  -1 */    -1,	// identity value
 	/*   0 */	  0,   1,   2,   3,   4,   5,   6,   7,
 	/*   8 */	  8,   9,  10,  11,  12,  13,  14,  15,
 	/*  16 */	 16,  17,  18,  19,  20,  21,  22,  23,
@@ -98,7 +105,8 @@ const int gPosixToLowerMap[256] = {
 };
 
 
-const int gPosixToUpperMap[256] = {
+const int gPosixToUpperMap[257] = {
+	/*  -1 */    -1,	// identity value
 	/*   0 */	  0,   1,   2,   3,   4,   5,   6,   7,
 	/*   8 */	  8,   9,  10,  11,  12,  13,  14,  15,
 	/*  16 */	 16,  17,  18,  19,  20,  21,  22,  23,
@@ -267,6 +275,6 @@ const char* gPosixLanginfo[_NL_LANGINFO_LAST] = {
 }	// namespace BPrivate
 
 
-const unsigned short* 	__ctype_b 		= BPrivate::gPosixClassInfo;
-const int* 				__ctype_tolower = BPrivate::gPosixToLowerMap;
-const int* 				__ctype_toupper = BPrivate::gPosixToUpperMap;
+const unsigned short* 	__ctype_b 		= &BPrivate::gPosixClassInfo[1];
+const int* 				__ctype_tolower = &BPrivate::gPosixToLowerMap[1];
+const int* 				__ctype_toupper = &BPrivate::gPosixToUpperMap[1];
diff --git a/src/tests/system/libroot/posix/locale_test.cpp b/src/tests/system/libroot/posix/locale_test.cpp
index 63ce4a43e8..e2a62b6df4 100644
--- a/src/tests/system/libroot/posix/locale_test.cpp
+++ b/src/tests/system/libroot/posix/locale_test.cpp
@@ -691,24 +691,24 @@ test_ctype(const char* locale, const unsigned short int classInfos[],
 	printf("ctype of %s locale\n", locale);
 
 	int problemCount = 0;
-	for (int i = 0; i < 256; ++i) {
+	for (int i = -1; i < 256; ++i) {
 		unsigned short classInfo = determineFullClassInfo(i);
 
-		if (classInfo != classInfos[i]) {
-			printf("\tPROBLEM: %d = %x (expected %x)\n", i, classInfo,
-				classInfos[i]);
+		if (classInfo != classInfos[i + 1]) {
+			printf("\tPROBLEM: ctype(%d) = %x (expected %x)\n", i, classInfo,
+				classInfos[i + 1]);
 			problemCount++;
 		}
 		int lower = tolower(i);
-		if (lower != toLowerMap[i]) {
+		if (lower != toLowerMap[i + 1]) {
 			printf("\tPROBLEM: tolower(%d) = %x (expected %x)\n", i, lower,
-				toLowerMap[i]);
+				toLowerMap[i + 1]);
 			problemCount++;
 		}
 		int upper = toupper(i);
-		if (upper != toUpperMap[i]) {
+		if (upper != toUpperMap[i + 1]) {
 			printf("\tPROBLEM: toupper(%d) = %x (expected %x)\n", i, upper,
-				toUpperMap[i]);
+				toUpperMap[i + 1]);
 			problemCount++;
 		}
 	}
@@ -722,7 +722,8 @@ test_ctype(const char* locale, const unsigned short int classInfos[],
 void
 test_ctype()
 {
-	const unsigned short int classInfos_posix[256] = {
+	const unsigned short int classInfos_posix[257] = {
+		/*  -1 */   0,	// neutral value
 		/*   0 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
 		/*   8 */	_IScntrl, _ISblank|_IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl, _IScntrl,
 		/*  16 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
@@ -756,7 +757,8 @@ test_ctype()
 		/* 240 */	0, 0, 0, 0, 0, 0, 0, 0,
 		/* 248 */	0, 0, 0, 0, 0, 0, 0, 0,
 	};
-	const int toLowerMap_posix[256] = {
+	const int toLowerMap_posix[257] = {
+		/*  -1 */    -1,	// identity value
 		/*   0 */	  0,   1,   2,   3,   4,   5,   6,   7,
 		/*   8 */	  8,   9,  10,  11,  12,  13,  14,  15,
 		/*  16 */	 16,  17,  18,  19,  20,  21,  22,  23,
@@ -790,7 +792,8 @@ test_ctype()
 		/* 240 */	240, 241, 242, 243, 244, 245, 246, 247,
 		/* 248 */	248, 249, 250, 251, 252, 253, 254, 255,
 	};
-	const int toUpperMap_posix[256] = {
+	const int toUpperMap_posix[257] = {
+		/*  -1 */    -1,	// identity value
 		/*   0 */	  0,   1,   2,   3,   4,   5,   6,   7,
 		/*   8 */	  8,   9,  10,  11,  12,  13,  14,  15,
 		/*  16 */	 16,  17,  18,  19,  20,  21,  22,  23,
@@ -826,7 +829,8 @@ test_ctype()
 	};
 	test_ctype("POSIX", classInfos_posix, toLowerMap_posix, toUpperMap_posix);
 
-	const unsigned short int classInfos_de[256] = {
+	const unsigned short int classInfos_de[257] = {
+		/*  -1 */   0,	// neutral value
 		/*   0 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
 		/*   8 */	_IScntrl, _ISblank|_IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl, _IScntrl,
 		/*  16 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
@@ -860,7 +864,8 @@ test_ctype()
 		/* 240 */	_ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph,
 		/* 248 */	_ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower, _ISprint|_ISgraph|_ISalnum|_ISalpha|_ISlower,
 	};
-	const int toLowerMap_de[256] = {
+	const int toLowerMap_de[257] = {
+		/*  -1 */    -1,	// identity value
 		/*   0 */	  0,   1,   2,   3,   4,   5,   6,   7,
 		/*   8 */	  8,   9,  10,  11,  12,  13,  14,  15,
 		/*  16 */	 16,  17,  18,  19,  20,  21,  22,  23,
@@ -894,7 +899,8 @@ test_ctype()
 		/* 240 */	240, 241, 242, 243, 244, 245, 246, 247,
 		/* 248 */	248, 249, 250, 251, 252, 253, 254, 255,
 	};
-	const int toUpperMap_de[256] = {
+	const int toUpperMap_de[257] = {
+		/*  -1 */    -1,	// identity value
 		/*   0 */	  0,   1,   2,   3,   4,   5,   6,   7,
 		/*   8 */	  8,   9,  10,  11,  12,  13,  14,  15,
 		/*  16 */	 16,  17,  18,  19,  20,  21,  22,  23,
@@ -930,7 +936,8 @@ test_ctype()
 	};
 	test_ctype("de_DE.ISO8859-1", classInfos_de, toLowerMap_de, toUpperMap_de);
 
-	const unsigned short int classInfos_utf8[256] = {
+	const unsigned short int classInfos_utf8[257] = {
+		/*  -1 */   0,	// neutral value
 		/*   0 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
 		/*   8 */	_IScntrl, _ISblank|_IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl|_ISspace, _IScntrl, _IScntrl,
 		/*  16 */	_IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl, _IScntrl,
@@ -1014,9 +1021,14 @@ test_wctype(const char* locale, const wchar_t* text,
 	printf("wctype of %s locale\n", locale);
 
 	int problemCount = 0;
+	unsigned short classInfo = determineWideFullClassInfo(WEOF);
+	if (classInfo != 0) {
+		printf("\tPROBLEM: classinfo for WEOF = %x (expected 0)\n", classInfo);
+		problemCount++;
+	}
 	wint_t wc = *text;
 	for (int i = 0; i < 48; wc = *++text, ++i) {
-		unsigned short classInfo = determineWideFullClassInfo(wc);
+		classInfo = determineWideFullClassInfo(wc);
 		if (wc != wcs[i]) {
 			printf("\tPROBLEM: wc for char #%d = %x (expected %x)\n", i, wc,
 				wcs[i]);