diff --git a/pbx.c b/pbx.c
index cef327d42aab78f099f03a5aa0c567eb438e8c2c..458f9d707de719f904baaf011ad33a8cb8ab2e8b 100644
--- a/pbx.c
+++ b/pbx.c
@@ -222,6 +222,7 @@ static int pbx_builtin_sayphonetic(struct ast_channel *, void *);
 int pbx_builtin_setvar(struct ast_channel *, void *);
 static int pbx_builtin_importvar(struct ast_channel *, void *);
 
+AST_MUTEX_DEFINE_STATIC(globalslock);
 static struct varshead globals;
 
 static int autofallthrough = 0;
@@ -974,12 +975,16 @@ void pbx_retrieve_variable(struct ast_channel *c, const char *var, char **ret, c
 		struct ast_var_t *variables;
 		if (!places[i])
 			continue;
+		if (places[i] == &globals)
+			ast_mutex_lock(&globalslock);
 		AST_LIST_TRAVERSE(places[i], variables, entries) {
 			if (strcasecmp(ast_var_name(variables), var)==0) {
 				s = ast_var_value(variables);
 				break;
 			}
 		}
+		if (places[i] == &globals)
+			ast_mutex_unlock(&globalslock);
 	}
 	if (s == &not_found || s == NULL)
 		*ret = NULL;
@@ -4390,10 +4395,12 @@ int ast_add_extension2(struct ast_context *con,
 	/* if we are adding a hint, and there are global variables, and the hint
 	   contains variable references, then expand them
 	*/
+	ast_mutex_lock(&globalslock);
 	if ((priority == PRIORITY_HINT) && AST_LIST_FIRST(&globals) && strstr(application, "${")) {
 		pbx_substitute_variables_varshead(&globals, application, expand_buf, sizeof(expand_buf));
 		application = expand_buf;
 	}
+	ast_mutex_unlock(&globalslock);
 
 	length = sizeof(struct ast_exten);
 	length += strlen(extension) + 1;
@@ -5500,6 +5507,7 @@ int pbx_builtin_serialize_variables(struct ast_channel *chan, char *buf, size_t
 const char *pbx_builtin_getvar_helper(struct ast_channel *chan, const char *name) 
 {
 	struct ast_var_t *variables;
+	const char *ret = NULL;
 	int i;
 	struct varshead *places[2] = { NULL, &globals };
 	
@@ -5509,14 +5517,23 @@ const char *pbx_builtin_getvar_helper(struct ast_channel *chan, const char *name
 		places[0] = &chan->varshead;
 
 	for (i = 0; i < 2; i++) {
-		if (places[i]) {
-			AST_LIST_TRAVERSE(places[i], variables, entries) {
-				if (!strcmp(name, ast_var_name(variables)))
-					return ast_var_value(variables);
+		if (!places[i])
+			continue;
+		if (places[i] == &globals)
+			ast_mutex_lock(&globalslock);
+		AST_LIST_TRAVERSE(places[i], variables, entries) {
+			if (!strcmp(name, ast_var_name(variables))) {
+				ret = ast_var_value(variables);
+				break;
 			}
 		}
+		if (places[i] == &globals)
+			ast_mutex_unlock(&globalslock);
+		if (ret)
+			break;
 	}
-	return NULL;
+
+	return ret;
 }
 
 void pbx_builtin_pushvar_helper(struct ast_channel *chan, const char *name, const char *value)
@@ -5537,8 +5554,12 @@ void pbx_builtin_pushvar_helper(struct ast_channel *chan, const char *name, cons
 	if (value) {
 		if ((option_verbose > 1) && (headp == &globals))
 			ast_verbose(VERBOSE_PREFIX_2 "Setting global variable '%s' to '%s'\n", name, value);
-		newvariable = ast_var_assign(name, value);	
+		newvariable = ast_var_assign(name, value);
+		if (headp == &globals)
+			ast_mutex_lock(&globalslock);
 		AST_LIST_INSERT_HEAD(headp, newvariable, entries);
+		if (headp == &globals)
+			ast_mutex_unlock(&globalslock);
 	}
 }
 
@@ -5564,6 +5585,8 @@ void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 			nametail++;
 	}
 
+	if (headp == &globals)
+		ast_mutex_lock(&globalslock);
 	AST_LIST_TRAVERSE (headp, newvariable, entries) {
 		if (strcasecmp(ast_var_name(newvariable), nametail) == 0) {
 			/* there is already such a variable, delete it */
@@ -5571,14 +5594,17 @@ void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 			ast_var_delete(newvariable);
 			break;
 		}
-	} 
-
+	}
+	
 	if (value) {
 		if ((option_verbose > 1) && (headp == &globals))
 			ast_verbose(VERBOSE_PREFIX_2 "Setting global variable '%s' to '%s'\n", name, value);
 		newvariable = ast_var_assign(name, value);	
 		AST_LIST_INSERT_HEAD(headp, newvariable, entries);
 	}
+	
+	if (headp == &globals)
+		ast_mutex_unlock(&globalslock);
 }
 
 int pbx_builtin_setvar(struct ast_channel *chan, void *data)
@@ -5681,10 +5707,11 @@ static int pbx_builtin_noop(struct ast_channel *chan, void *data)
 void pbx_builtin_clear_globals(void)
 {
 	struct ast_var_t *vardata;
-	while (!AST_LIST_EMPTY(&globals)) {
-		vardata = AST_LIST_REMOVE_HEAD(&globals, entries);
+
+	ast_mutex_lock(&globalslock);
+	while ((vardata = AST_LIST_REMOVE_HEAD(&globals, entries)))
 		ast_var_delete(vardata);
-	}
+	ast_mutex_unlock(&globalslock);
 }
 
 static int pbx_checkcondition(char *condition)