diff --git a/configure.ac b/configure.ac
index 7158f20..5d4c10b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,5 +1,6 @@
 AC_INIT([r3], 1.0.0)
 AC_PREREQ([2.64])
+AC_USE_SYSTEM_EXTENSIONS
 AC_CONFIG_HEADERS(config.h)
 AC_CONFIG_MACRO_DIR([m4])
 AM_INIT_AUTOMAKE([foreign subdir-objects])
@@ -18,9 +19,6 @@ AC_TYPE_SIZE_T
 AC_FUNC_MALLOC
 AC_FUNC_REALLOC
 AC_CHECK_FUNCS([gettimeofday memset strchr strdup strndup strstr])
-
-
-
 PKG_PROG_PKG_CONFIG
 
 
diff --git a/src/slug.c b/src/slug.c
index fdd039a..d19df8a 100644
--- a/src/slug.c
+++ b/src/slug.c
@@ -4,6 +4,7 @@
  *
  * Distributed under terms of the MIT license.
  */
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include "config.h"
@@ -19,6 +20,8 @@ inline int contains_slug_char(const char * str) {
 
 r3_slug_t * r3_slug_new(char * path, int path_len) {
     r3_slug_t * s = zmalloc(sizeof(r3_slug_t));
+    if (!s)
+        return NULL;
     s->path = path;
     s->path_len = path_len;
 
diff --git a/tests/check_slug.c b/tests/check_slug.c
index bae4d42..aeb0544 100644
--- a/tests/check_slug.c
+++ b/tests/check_slug.c
@@ -100,11 +100,13 @@ START_TEST (test_slug_parse_with_pattern)
 {
     char * pattern = "/user/{name:\\d{3}}";
     char * errstr = NULL;
-    r3_slug_t *s = r3_slug_parse(pattern, strlen(pattern), pattern, &errstr);
+    const r3_slug_t *s = r3_slug_parse(pattern, strlen(pattern), pattern, &errstr);
+    ck_assert(s);
 
     char * out = r3_slug_to_str(s);
+    ck_assert(out);
     printf("%s\n",out);
-    zfree(out);
+    free(out);
 
     r3_slug_free(s);
 }
@@ -115,11 +117,13 @@ START_TEST (test_slug_parse_without_pattern)
 {
     char * pattern = "/user/{name}";
     char * errstr = NULL;
-    r3_slug_t *s = r3_slug_parse(pattern, strlen(pattern), pattern, &errstr);
+    const r3_slug_t *s = r3_slug_parse(pattern, strlen(pattern), pattern, &errstr);
+    ck_assert(s);
 
     char * out = r3_slug_to_str(s);
+    ck_assert(out);
     printf("%s\n",out);
-    zfree(out);
+    free(out);
 
     r3_slug_free(s);
 }