diff --git a/src/util/misc.c b/src/util/misc.c
index 805a086..b0ab2f9 100644
--- a/src/util/misc.c
+++ b/src/util/misc.c
@@ -63,7 +63,7 @@ char* strip_white_space(char* string)
 	return string;
 }
 
-static int is_valid_utf8_str(const char* string, size_t length)
+static int is_valid_utf8_str(const unsigned char* string, size_t length)
 {
 	int expect = 0;
 	char div = 0;
@@ -82,12 +82,32 @@ static int is_valid_utf8_str(const char* string, size_t length)
 		{
 			if (string[pos] & 0x80)
 			{
-				for (div = 0x40; div > 0x10; div /= 2)
+				for (div = 0x40; div > 0x08; div /= 2)
 				{
 					if (string[pos] & div) expect++;
 					else break;
 				}
 				if ((string[pos] & div) || (pos+expect >= length)) return 0;
+				switch (expect) {
+					case 0:
+						return 0;
+					case 1:
+						/* Out of range */
+						if (string[pos] < 0xC2) return 0;
+						break;
+					case 2:
+						/* Out of range */
+						if ((string[pos] == 0xE0) && (string[pos+1] < 0xA0 )) return 0;
+						/* Surrogates */
+						if ((string[pos] == 0xED) && (string[pos+1] > 0x9F )) return 0;
+						break;
+					case 3:
+						/* Out of range */
+						if ((string[pos] == 0xF0) && (string[pos+1] < 0x90 )) return 0;
+						if (string[pos] > 0xF4) return 0;
+						if ((string[pos] == 0xF4) && (string[pos+1] > 0x8F )) return 0;
+						break;
+				}
 			}
 		}
 	}