diff --git a/syscall_filter.c b/syscall_filter.c
index 956fe21..9a66d17 100644
--- a/syscall_filter.c
+++ b/syscall_filter.c
@@ -254,7 +254,7 @@
 
 int compile_errno(struct filter_block *head, char *ret_errno, int use_ret_trap)
 {
-	char *errno_ptr;
+	char *errno_ptr = NULL;
 
 	/* Splits the 'return' keyword and the actual errno value. */
 	char *ret_str = strtok_r(ret_errno, " ", &errno_ptr);