diff --git a/include/set_asserts.h b/include/set_asserts.h
index 32d9209..c65a2a6 100644
--- a/include/set_asserts.h
+++ b/include/set_asserts.h
@@ -28,8 +28,9 @@
     if (exp != act)                                                            \
     {                                                                          \
         test->passed = false;                                                  \
-        test->error_msg = format_string(                                       \
-            "Expected %d to be %d\n    Failed with message: " msg, act, exp);  \
+        test->error_msg =                                                      \
+            format_string("Expected %d to be %d\n    Failed with message: %s", \
+                          act, exp, msg);                                      \
         return;                                                                \
     }
 
diff --git a/src/list.c b/src/list.c
index e182b59..b45e0bc 100644
--- a/src/list.c
+++ b/src/list.c
@@ -28,8 +28,11 @@ struct SETBlockMeta *set_ll_free_one(struct SETBlockMeta *head, void *address)
     if (meta == head)
     {
         struct SETBlockMeta *ret = meta->next;
-        ret->prev = NULL;
-        ret->end = meta->end;
+        if (ret)
+        {
+            ret->prev = NULL;
+            ret->end = meta->end;
+        }
         free(meta);
         return ret;
     }
diff --git a/src/utils.c b/src/utils.c
index 1a693a5..a3266c1 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -15,7 +15,7 @@ char *format_string(const char *fmt, ...)
     va_list args;
     va_start(args, fmt);
     size_t size = vsnprintf(NULL, 0, fmt, args);
-    char *out = (char *)malloc(size + 1);
+    char *out = (char *)set_malloc(size + 1);
 
     if (!out)
     {
diff --git a/testtest.c b/testtest.c
index 3d875c8..8ab5800 100644
--- a/testtest.c
+++ b/testtest.c
@@ -61,6 +61,7 @@ TEST(Other_Basic)
 TEST(Other_With_Malloc)
 {
     int *some_array = set_malloc(20 * sizeof(int));
+    int *array = set_malloc(20);
 
     for (int i = 0; i < 20; i++)
     {
@@ -73,6 +74,9 @@ TEST(Other_With_Malloc)
     }
     fprintf(stdout, ".\n");
 
+    set_free(array);
+    set_free(some_array);
+
     ASSERT_TRUE(false);
 }