diff --git a/aegisub/libaegisub/Makefile b/aegisub/libaegisub/Makefile
index b7b85465a..374ea516d 100644
--- a/aegisub/libaegisub/Makefile
+++ b/aegisub/libaegisub/Makefile
@@ -31,6 +31,7 @@ SRC = \
 	common/path.cpp \
 	common/progress.cpp \
 	common/keyframe.cpp \
+	common/util.cpp \
 	common/log.cpp \
 	common/validator.cpp \
 	common/vfr.cpp \
diff --git a/aegisub/libaegisub/common/util.cpp b/aegisub/libaegisub/common/util.cpp
new file mode 100644
index 000000000..3b23a562d
--- /dev/null
+++ b/aegisub/libaegisub/common/util.cpp
@@ -0,0 +1,39 @@
+// Copyright (c) 2011, Amar Takhar <verm@aegisub.org>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+// $Id$
+
+/// @file util.cpp
+/// @brief Unix utility methods.
+/// @ingroup libaegisub
+
+#ifndef LAGI_PRE
+#endif
+
+#include <locale>
+
+#include "libaegisub/util.h"
+
+namespace agi {
+	namespace util {
+
+
+void str_lower(std::string &str) {
+	for (size_t i=0; i < str.length(); ++i) {
+		str[i] = std::tolower(str[i]);
+	}
+}
+
+	} // namespace util
+} // namespace agi
diff --git a/aegisub/libaegisub/include/libaegisub/util.h b/aegisub/libaegisub/include/libaegisub/util.h
index fecc1c762..13ddefe95 100644
--- a/aegisub/libaegisub/include/libaegisub/util.h
+++ b/aegisub/libaegisub/include/libaegisub/util.h
@@ -37,6 +37,7 @@ namespace agi {
 	const std::string DirName(const std::string& path);
 	void Rename(const std::string& from, const std::string& to);
 	void time_log(agi_timeval &tv);
+	void str_lower(std::string &str);
 
 	struct delete_ptr {
 		template<class T>