diff --git a/libs/ruamoko/rua_string.c b/libs/ruamoko/rua_string.c
index 31b717273..754d1627e 100644
--- a/libs/ruamoko/rua_string.c
+++ b/libs/ruamoko/rua_string.c
@@ -265,6 +265,22 @@ bi_str_lower (progs_t *pr)
 	RETURN_STRING (pr, lower);
 }
 
+static void
+bi_str_upper (progs_t *pr)
+{
+	const char *str = P_GSTRING (pr, 0);
+	char       *upper = alloca (strlen (str) + 1);
+	char       *l = upper;
+	byte        c;
+
+	while ((c = *str++)) {
+		*l++ = toupper (c);
+	}
+	*l++ = 0;
+
+	RETURN_STRING (pr, upper);
+}
+
 static builtin_t builtins[] = {
 	{"strlen",		bi_strlen,		-1},
 	{"sprintf",		bi_sprintf,		-1},
@@ -283,6 +299,7 @@ static builtin_t builtins[] = {
 	{"str_char",	bi_str_char,	-1},
 	{"str_quote",	bi_str_quote,	-1},
 	{"str_lower",	bi_str_lower,	-1},
+	{"str_upper",	bi_str_upper,	-1},
 	{0}
 };
 
diff --git a/ruamoko/include/string.h b/ruamoko/include/string.h
index 8087ef67e..3d978cfd5 100644
--- a/ruamoko/include/string.h
+++ b/ruamoko/include/string.h
@@ -18,5 +18,6 @@ int str_str (string haystack, string needle);
 @extern int str_char (string str, int ind);
 string str_quote (string str);
 string str_lower (string str);
+string str_upper (string str);
 
 #endif//__ruamoko_string_h
diff --git a/ruamoko/lib/string.r b/ruamoko/lib/string.r
index 3858ef7d6..5169296a0 100644
--- a/ruamoko/lib/string.r
+++ b/ruamoko/lib/string.r
@@ -17,3 +17,4 @@ int str_str (string haystack, string needle) = #0;
 int str_char (string str, int ind) = #0;
 string str_quote (string str) = #0;
 string str_lower (string str) = #0;
+string str_upper (string str) = #0;