diff --git a/src/helpers.h b/src/helpers.h
index d850851..876a353 100644
--- a/src/helpers.h
+++ b/src/helpers.h
@@ -44,4 +44,7 @@ extern vmod_state_t vmod_state;
 #define FAIL_WS(ctx, result) \
     FAIL(ctx, result, "Workspace overflow")
 
+#define FAIL_INSTANCE(ctx, result) \
+    FAIL(ctx, result, "Failed to create instance")
+
 #endif
diff --git a/src/vmod_cfg_file.c b/src/vmod_cfg_file.c
index 5a33ae4..c191e2e 100644
--- a/src/vmod_cfg_file.c
+++ b/src/vmod_cfg_file.c
@@ -358,6 +358,10 @@ vmod_file__init(
         }
     }
 
+    if (instance == NULL) {
+        FAIL_INSTANCE(ctx,);
+    }
+
     *file = instance;
 }
 
diff --git a/src/vmod_cfg_rules.c b/src/vmod_cfg_rules.c
index 10027d2..383ba51 100644
--- a/src/vmod_cfg_rules.c
+++ b/src/vmod_cfg_rules.c
@@ -265,6 +265,10 @@ vmod_rules__init(
         }
     }
 
+    if (instance == NULL) {
+        FAIL_INSTANCE(ctx,);
+    }
+
     *rules = instance;
 }
 
diff --git a/src/vmod_cfg_script.c b/src/vmod_cfg_script.c
index fba32ca..5add701 100644
--- a/src/vmod_cfg_script.c
+++ b/src/vmod_cfg_script.c
@@ -151,6 +151,10 @@ vmod_script__init(
         }
     }
 
+    if (instance == NULL) {
+        FAIL_INSTANCE(ctx,);
+    }
+
     *script = instance;
 }