diff --git a/lib/flow_runner/spec/block.ex b/lib/flow_runner/spec/block.ex
index c1ae4a5..565c6ce 100644
--- a/lib/flow_runner/spec/block.ex
+++ b/lib/flow_runner/spec/block.ex
@@ -54,11 +54,16 @@ defmodule FlowRunner.Spec.Block do
 
     * `{:invalid, reason}` — the flow runner will exit through the
       block's default response.
+
+    * `{:error, reason}` — the block could not pick an exit at all (for
+      example a `Core.Case` whose tests all evaluated to false and which
+      has no default exit); the error is returned to the caller.
   """
   @callback evaluate_outgoing(Container.t(), Flow.t(), Block.t(), Context.t(), user_input :: any) ::
               {:ok, user_input :: any}
               | {:ok, user_input :: any, opts :: Keyword.t()}
               | {:invalid, reason :: String.t()}
+              | {:error, reason :: String.t()}
 
   @derive Jason.Encoder
   defstruct uuid: nil,
@@ -228,7 +233,9 @@ defmodule FlowRunner.Spec.Block do
 
   @decorate with_span("FlowRunner.Spec.Block.evaluate_outgoing")
   @spec evaluate_outgoing(Container.t(), Flow.t(), Block.t(), Context.t(), user_input :: any) ::
-          {:ok, Context.t(), Block.t()} | {:invalid, reason :: String.t()}
+          {:ok, Context.t(), Block.t() | nil}
+          | {:invalid, reason :: String.t()}
+          | {:error, reason :: String.t()}
   def evaluate_outgoing(
         container,
         flow,
@@ -270,12 +277,16 @@ defmodule FlowRunner.Spec.Block do
         {:ok, context} = evaluate_user_input(block, context, user_input)
 
         fetch_default_block(block, flow, context)
+
+      {:error, reason} ->
+        {:error, reason}
     end
   end
 
   defp normalize_outgoing({:ok, user_input}), do: {:ok, user_input, []}
   defp normalize_outgoing({:ok, user_input, opts}) when is_list(opts), do: {:ok, user_input, opts}
   defp normalize_outgoing({:invalid, _} = invalid), do: invalid
+  defp normalize_outgoing({:error, _} = error), do: error
 
   @spec fetch_default_block(Block.t(), Flow.t(), Context.t()) ::
           {:error, String.t()} | {:ok, Context.t(), Block.t() | nil}
diff --git a/lib/flow_runner/spec/blocks/case.ex b/lib/flow_runner/spec/blocks/case.ex
index b1ac3b4..49d2571 100644
--- a/lib/flow_runner/spec/blocks/case.ex
+++ b/lib/flow_runner/spec/blocks/case.ex
@@ -33,14 +33,14 @@ defmodule FlowRunner.Spec.Blocks.Case do
 
   @impl FlowRunner.Spec.Block
   def evaluate_outgoing(_container, _flow, block, context, nil) do
-    {:ok, block_exit} = Block.evaluate_exits(block, context)
-
-    case FlowRunner.evaluate_expression_block(block_exit.name, context) do
-      # We didn't manage to parse it and it returned a parsing error
-      {:error, _error, _reason} -> {:ok, block_exit.name}
-      # We managed to evaluate it and it returned nil
-      nil -> {:ok, block_exit.name}
-      value -> {:ok, value}
+    with {:ok, block_exit} <- Block.evaluate_exits(block, context) do
+      case FlowRunner.evaluate_expression_block(block_exit.name, context) do
+        # We didn't manage to parse it and it returned a parsing error
+        {:error, _error, _reason} -> {:ok, block_exit.name}
+        # We managed to evaluate it and it returned nil
+        nil -> {:ok, block_exit.name}
+        value -> {:ok, value}
+      end
     end
   end
 end
diff --git a/mix.exs b/mix.exs
index 506893b..03fa3d5 100644
--- a/mix.exs
+++ b/mix.exs
@@ -1,7 +1,7 @@
 defmodule FlowRunner.MixProject do
   use Mix.Project
 
-  @version "6.15.1"
+  @version "6.15.2"
 
   def project do
     [
diff --git a/test/block_test.exs b/test/block_test.exs
index f889e56..ebeb6c1 100644
--- a/test/block_test.exs
+++ b/test/block_test.exs
@@ -4,6 +4,7 @@ defmodule BlockTest do
 
   alias FlowRunner.Context
   alias FlowRunner.Spec.Block
+  alias FlowRunner.Spec.Container
   alias FlowRunner.Spec.Exit
   alias FlowRunner.Spec.Flow
 
@@ -259,6 +260,66 @@ defmodule BlockTest do
     assert {:ok, %Exit{uuid: "failure-exit"}} = Block.evaluate_exits(block, context_false)
   end
 
+  describe "evaluate_outgoing/5 on a Core.Case block" do
+    test "returns an error instead of raising when no exit matches and there is no default exit" do
+      routing_block = %Block{
+        uuid: "5a0a4c1e-1d0e-4a4e-9a8e-3c1d7b2f6e01",
+        name: "Routing for check",
+        type: "Core.Case",
+        exits: [
+          %Exit{
+            uuid: "b586afa7-0097-4805-9951-f6d3156c08db",
+            name: "Exit for CheckYes",
+            test: "block.value = 5",
+            destination_block: "8e2f8c2d-4b0b-4a3f-8a6c-1f2e3d4c5b6a"
+          }
+        ]
+      }
+
+      context = %Context{vars: %{"block" => %{"value" => 10}}}
+
+      assert {:error, "No default exit available"} =
+               Block.evaluate_outgoing(
+                 %Container{},
+                 %Flow{blocks: [routing_block]},
+                 routing_block,
+                 context,
+                 nil
+               )
+    end
+
+    test "stores the exit name when the name evaluates to nil" do
+      destination_uuid = "8e2f8c2d-4b0b-4a3f-8a6c-1f2e3d4c5b6a"
+
+      routing_block = %Block{
+        uuid: "5a0a4c1e-1d0e-4a4e-9a8e-3c1d7b2f6e02",
+        name: "Routing for check",
+        type: "Core.Case",
+        exits: [
+          %Exit{
+            uuid: "c2f1e9a0-6d3b-4f8e-9c1a-2b3d4e5f6a70",
+            name: "answer",
+            test: "true",
+            destination_block: destination_uuid
+          }
+        ]
+      }
+
+      destination_block = %Block{uuid: destination_uuid, name: "destination", type: "Core.Log"}
+      context = %Context{vars: %{"answer" => nil}}
+
+      assert {:ok, %Context{vars: %{"Routing for check" => "answer"}},
+              %Block{uuid: ^destination_uuid}} =
+               Block.evaluate_outgoing(
+                 %Container{},
+                 %Flow{blocks: [routing_block, destination_block]},
+                 routing_block,
+                 context,
+                 nil
+               )
+    end
+  end
+
   describe "load_config_for_set_contact_property!/1" do
     test "accepts the singular shape" do
       assert %{