Index: boot/generic/src/str.c
===================================================================
--- boot/generic/src/str.c	(revision a4a0f1d7c7494d19298310f3c5aee2ec5b01e30b)
+++ boot/generic/src/str.c	(revision 8e893aeb5653f1350d4daa8ac443ec24ef6449cd)
@@ -100,4 +100,11 @@
 #include <str.h>
 #include <errno.h>
+
+/** Check the condition if wchar_t is signed */
+#ifdef WCHAR_IS_UNSIGNED
+	#define WCHAR_SIGNED_CHECK(cond)  (true)
+#else
+	#define WCHAR_SIGNED_CHECK(cond)  (cond)
+#endif
 
 /** Byte mask consisting of lowest @n bits (out of 8) */
@@ -198,5 +205,5 @@
  *         code was invalid.
  */
-int chr_encode(wchar_t ch, char *str, size_t *offset, size_t size)
+int chr_encode(const wchar_t ch, char *str, size_t *offset, size_t size)
 {
 	if (*offset >= size)
@@ -325,5 +332,5 @@
 bool ascii_check(wchar_t ch)
 {
-	if ((ch >= 0) && (ch <= 127))
+	if (WCHAR_SIGNED_CHECK(ch >= 0) && (ch <= 127))
 		return true;
 	
@@ -338,5 +345,5 @@
 bool chr_check(wchar_t ch)
 {
-	if ((ch >= 0) && (ch <= 1114111))
+	if (WCHAR_SIGNED_CHECK(ch >= 0) && (ch <= 1114111))
 		return true;
 	
Index: kernel/generic/src/lib/str.c
===================================================================
--- kernel/generic/src/lib/str.c	(revision a4a0f1d7c7494d19298310f3c5aee2ec5b01e30b)
+++ kernel/generic/src/lib/str.c	(revision 8e893aeb5653f1350d4daa8ac443ec24ef6449cd)
@@ -111,4 +111,11 @@
 #include <debug.h>
 #include <macros.h>
+
+/** Check the condition if wchar_t is signed */
+#ifdef WCHAR_IS_UNSIGNED
+	#define WCHAR_SIGNED_CHECK(cond)  (true)
+#else
+	#define WCHAR_SIGNED_CHECK(cond)  (cond)
+#endif
 
 /** Byte mask consisting of lowest @n bits (out of 8) */
@@ -206,8 +213,8 @@
  *
  * @return EOK if the character was encoded successfully, EOVERFLOW if there
- *	   was not enough space in the output buffer or EINVAL if the character
- *	   code was invalid.
- */
-int chr_encode(wchar_t ch, char *str, size_t *offset, size_t size)
+ *         was not enough space in the output buffer or EINVAL if the character
+ *         code was invalid.
+ */
+int chr_encode(const wchar_t ch, char *str, size_t *offset, size_t size)
 {
 	if (*offset >= size)
@@ -427,5 +434,5 @@
 bool ascii_check(wchar_t ch)
 {
-	if ((ch >= 0) && (ch <= 127))
+	if (WCHAR_SIGNED_CHECK(ch >= 0) && (ch <= 127))
 		return true;
 	
@@ -440,5 +447,5 @@
 bool chr_check(wchar_t ch)
 {
-	if ((ch >= 0) && (ch <= 1114111))
+	if (WCHAR_SIGNED_CHECK(ch >= 0) && (ch <= 1114111))
 		return true;
 	
Index: uspace/lib/c/generic/str.c
===================================================================
--- uspace/lib/c/generic/str.c	(revision a4a0f1d7c7494d19298310f3c5aee2ec5b01e30b)
+++ uspace/lib/c/generic/str.c	(revision 8e893aeb5653f1350d4daa8ac443ec24ef6449cd)
@@ -46,4 +46,11 @@
 #include <mem.h>
 #include <str.h>
+
+/** Check the condition if wchar_t is signed */
+#ifdef WCHAR_IS_UNSIGNED
+	#define WCHAR_SIGNED_CHECK(cond)  (true)
+#else
+	#define WCHAR_SIGNED_CHECK(cond)  (cond)
+#endif
 
 /** Byte mask consisting of lowest @n bits (out of 8) */
@@ -399,5 +406,5 @@
 bool ascii_check(wchar_t ch)
 {
-	if ((ch >= 0) && (ch <= 127))
+	if (WCHAR_SIGNED_CHECK(ch >= 0) && (ch <= 127))
 		return true;
 	
@@ -412,5 +419,5 @@
 bool chr_check(wchar_t ch)
 {
-	if ((ch >= 0) && (ch <= 1114111))
+	if (WCHAR_SIGNED_CHECK(ch >= 0) && (ch <= 1114111))
 		return true;
 	
@@ -513,4 +520,5 @@
  * @param count Size of the destination buffer (must be > 0).
  * @param src   Source string.
+ *
  */
 void str_cpy(char *dest, size_t size, const char *src)
@@ -545,4 +553,5 @@
  * @param src   Source string.
  * @param n     Maximum number of bytes to read from @a src.
+ *
  */
 void str_ncpy(char *dest, size_t size, const char *src, size_t n)