diff --git a/libs/backends/jack/jack_utils.cc b/libs/backends/jack/jack_utils.cc
index 66255968e0..f7d75a4a79 100644
--- a/libs/backends/jack/jack_utils.cc
+++ b/libs/backends/jack/jack_utils.cc
@@ -631,9 +631,16 @@ ARDOUR::get_jack_default_server_path (std::string& server_path)
 	return true;
 }
 
-string
-quote_string (const string& str)
+static string
+quote_string (string str)
 {
+	/* escape quotes in string */
+	size_t pos = 0;
+	while ((pos = str.find("\"", pos)) != std::string::npos) {
+		str.replace (pos, 1, "\\\"");
+		pos += 2;
+	}
+	/* and quote the whole string */
 	return "\"" + str + "\"";
 }
 
diff --git a/libs/pbd/system_exec.cc b/libs/pbd/system_exec.cc
index d1079a311f..cec58504ae 100644
--- a/libs/pbd/system_exec.cc
+++ b/libs/pbd/system_exec.cc
@@ -215,8 +215,11 @@ SystemExec::SystemExec (std::string command, const std::map<char, std::string> s
 		// ...but always quote all args
 		for (int i = 1; argp[i]; ++i) {
 			std::string tmp (argp[i]);
-			while (tmp.find("\"") != std::string::npos)
-				tmp.replace(tmp.find("\""), 1, "\\\"");
+			size_t start_pos = 0;
+			while ((start_pos = tmp.find("\"", start_pos)) != std::string::npos) {
+				tmp.replace (start_pos, 1, "\\\"");
+				start_pos += 2;
+			}
 			wa += " \"";
 			wa += tmp;
 			wa += '"';