diff --git a/cardano-cli/test/cardano-cli-golden/Test/Golden/Governance/Action.hs b/cardano-cli/test/cardano-cli-golden/Test/Golden/Governance/Action.hs
index 5297b3e1ba..3ec4298fb3 100644
--- a/cardano-cli/test/cardano-cli-golden/Test/Golden/Governance/Action.hs
+++ b/cardano-cli/test/cardano-cli-golden/Test/Golden/Governance/Action.hs
@@ -9,6 +9,8 @@ import           Cardano.Api (MonadIO)
 import           Control.Monad (void)
 import           Control.Monad.Catch (MonadCatch)
 import           Control.Monad.Trans.Control (MonadBaseControl)
+import           Data.List (isInfixOf)
+import           System.Exit (ExitCode (ExitSuccess))
 
 import           Test.Cardano.CLI.Hash (exampleAnchorDataHash, exampleAnchorDataHash2,
                    exampleAnchorDataIpfsHash, exampleAnchorDataIpfsHash2,
@@ -497,6 +499,50 @@ hprop_golden_conway_governance_action_create_protocol_parameters_update_partial_
         "test/cardano-cli-golden/files/golden/governance/action/conway-create-protocol-parameters-update-partial-costmodels.action"
     H.diffFileVsGoldenFile actionFile goldenActionFile
 
+-- | Execute me with:
+-- @cabal test cardano-cli-golden --test-options '-p "/golden conway governance action create protocol parameters bad costmodel size/"'@
+hprop_golden_conway_governance_action_create_protocol_parameters_bad_costmodel_size
+  :: Property
+hprop_golden_conway_governance_action_create_protocol_parameters_bad_costmodel_size =
+  propertyOnce . H.moduleWorkspace "tmp" $ \tempDir -> do
+    -- This file has 184 entries, whereas PV1 requires 166
+    -- TODO @smelc this test does not pass: the command succeeds, whereas it should fail!
+    -- runOnCostModelFile tempDir "test/cardano-cli-golden/files/input/governance/costmodels-v1-wrong.json"
+    -- This file has 184 entries, whereas PV2 requires 185
+    runOnCostModelFile tempDir "test/cardano-cli-golden/files/input/governance/costmodels-v2-wrong.json"
+    -- This file has 184 entries, whereas PV3 requires 297
+    runOnCostModelFile tempDir "test/cardano-cli-golden/files/input/governance/costmodels-v3-wrong.json"
+ where
+  runOnCostModelFile tempDir costModelsFile = do
+    stakeAddressVKeyFile <- H.note "test/cardano-cli-golden/files/input/governance/stake-address.vkey"
+
+    actionFile <- noteTempFile tempDir "action"
+
+    (exitCode, _stdout, stderr) <-
+      H.noteShowM $
+        H.execDetailCardanoCLI
+          [ "conway"
+          , "governance"
+          , "action"
+          , "create-protocol-parameters-update"
+          , "--anchor-url"
+          , "example.com"
+          , "--anchor-data-hash"
+          , "c7ddb5b493faa4d3d2d679847740bdce0c5d358d56f9b1470ca67f5652a02745"
+          , "--mainnet"
+          , "--deposit-return-stake-verification-key-file"
+          , stakeAddressVKeyFile
+          , "--governance-action-deposit"
+          , "12345"
+          , "--cost-model-file"
+          , costModelsFile
+          , "--out-file"
+          , actionFile
+          ]
+
+    H.assert (exitCode /= ExitSuccess)
+    H.assertWith stderr $ \msg -> "The decoded cost model has the wrong size" `isInfixOf` msg
+
 hprop_golden_conway_governance_action_create_hardfork_wrong_hash_fails :: Property
 hprop_golden_conway_governance_action_create_hardfork_wrong_hash_fails =
   propertyOnce . expectFailure . H.moduleWorkspace "tmp" $ \tempDir -> do
diff --git a/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v1-wrong.json b/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v1-wrong.json
new file mode 100644
index 0000000000..87bfe9b2f6
--- /dev/null
+++ b/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v1-wrong.json
@@ -0,0 +1,187 @@
+{ "PlutusV1": [
+		812,
+		1,
+		1,
+		1000,
+		571,
+		0,
+		1,
+		1000,
+		24177,
+		4,
+		1,
+		1000,
+		32,
+		117366,
+		10475,
+		4,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		100,
+		100,
+		23000,
+		100,
+		19537,
+		32,
+		175354,
+		32,
+		46417,
+		4,
+		221973,
+		511,
+		0,
+		1,
+		89141,
+		32,
+		497525,
+		14068,
+		4,
+		2,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		1000,
+		28662,
+		4,
+		2,
+		245000,
+		216773,
+		62,
+		1,
+		1060367,
+		12586,
+		1,
+		208512,
+		421,
+		1,
+		187000,
+		1000,
+		52998,
+		1,
+		80436,
+		32,
+		43249,
+		32,
+		1000,
+		32,
+		80556,
+		1,
+		57667,
+		4,
+		1000,
+		10,
+		197145,
+		156,
+		1,
+		197145,
+		156,
+		1,
+		204924,
+		473,
+		1,
+		208896,
+		511,
+		1,
+		52467,
+		32,
+		64832,
+		32,
+		65493,
+		32,
+		22558,
+		32,
+		16563,
+		32,
+		76511,
+		32,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		69522,
+		11687,
+		0,
+		1,
+		60091,
+		32,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		1159724,
+		392670,
+		0,
+		2,
+		806990,
+		30482,
+		4,
+		1927926,
+		82523,
+		4,
+		265318,
+		0,
+		4,
+		0,
+		85931,
+		32,
+		205665,
+		812,
+		1,
+		1,
+		41182,
+		32,
+		212342,
+		32,
+		31220,
+		32,
+		32696,
+		32,
+		43357,
+		32,
+		32247,
+		32,
+		38314,
+		32,
+		35892428,
+		10,
+		9462713,
+		1021,
+		10,
+		38887044,
+		32947,
+		10,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0
+  ]
+}
diff --git a/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v2-wrong.json b/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v2-wrong.json
new file mode 100644
index 0000000000..a953433332
--- /dev/null
+++ b/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v2-wrong.json
@@ -0,0 +1,187 @@
+{ "PlutusV2": [
+		812,
+		1,
+		1,
+		1000,
+		571,
+		0,
+		1,
+		1000,
+		24177,
+		4,
+		1,
+		1000,
+		32,
+		117366,
+		10475,
+		4,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		100,
+		100,
+		23000,
+		100,
+		19537,
+		32,
+		175354,
+		32,
+		46417,
+		4,
+		221973,
+		511,
+		0,
+		1,
+		89141,
+		32,
+		497525,
+		14068,
+		4,
+		2,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		1000,
+		28662,
+		4,
+		2,
+		245000,
+		216773,
+		62,
+		1,
+		1060367,
+		12586,
+		1,
+		208512,
+		421,
+		1,
+		187000,
+		1000,
+		52998,
+		1,
+		80436,
+		32,
+		43249,
+		32,
+		1000,
+		32,
+		80556,
+		1,
+		57667,
+		4,
+		1000,
+		10,
+		197145,
+		156,
+		1,
+		197145,
+		156,
+		1,
+		204924,
+		473,
+		1,
+		208896,
+		511,
+		1,
+		52467,
+		32,
+		64832,
+		32,
+		65493,
+		32,
+		22558,
+		32,
+		16563,
+		32,
+		76511,
+		32,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		69522,
+		11687,
+		0,
+		1,
+		60091,
+		32,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		1159724,
+		392670,
+		0,
+		2,
+		806990,
+		30482,
+		4,
+		1927926,
+		82523,
+		4,
+		265318,
+		0,
+		4,
+		0,
+		85931,
+		32,
+		205665,
+		812,
+		1,
+		1,
+		41182,
+		32,
+		212342,
+		32,
+		31220,
+		32,
+		32696,
+		32,
+		43357,
+		32,
+		32247,
+		32,
+		38314,
+		32,
+		35892428,
+		10,
+		9462713,
+		1021,
+		10,
+		38887044,
+		32947,
+		10,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0
+  ]
+}
diff --git a/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v3-wrong.json b/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v3-wrong.json
new file mode 100644
index 0000000000..fc000abaac
--- /dev/null
+++ b/cardano-cli/test/cardano-cli-golden/files/input/governance/costmodels-v3-wrong.json
@@ -0,0 +1,187 @@
+{ "PlutusV3": [
+		812,
+		1,
+		1,
+		1000,
+		571,
+		0,
+		1,
+		1000,
+		24177,
+		4,
+		1,
+		1000,
+		32,
+		117366,
+		10475,
+		4,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		23000,
+		100,
+		100,
+		100,
+		23000,
+		100,
+		19537,
+		32,
+		175354,
+		32,
+		46417,
+		4,
+		221973,
+		511,
+		0,
+		1,
+		89141,
+		32,
+		497525,
+		14068,
+		4,
+		2,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		1000,
+		28662,
+		4,
+		2,
+		245000,
+		216773,
+		62,
+		1,
+		1060367,
+		12586,
+		1,
+		208512,
+		421,
+		1,
+		187000,
+		1000,
+		52998,
+		1,
+		80436,
+		32,
+		43249,
+		32,
+		1000,
+		32,
+		80556,
+		1,
+		57667,
+		4,
+		1000,
+		10,
+		197145,
+		156,
+		1,
+		197145,
+		156,
+		1,
+		204924,
+		473,
+		1,
+		208896,
+		511,
+		1,
+		52467,
+		32,
+		64832,
+		32,
+		65493,
+		32,
+		22558,
+		32,
+		16563,
+		32,
+		76511,
+		32,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		69522,
+		11687,
+		0,
+		1,
+		60091,
+		32,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		196500,
+		453240,
+		220,
+		0,
+		1,
+		1,
+		1159724,
+		392670,
+		0,
+		2,
+		806990,
+		30482,
+		4,
+		1927926,
+		82523,
+		4,
+		265318,
+		0,
+		4,
+		0,
+		85931,
+		32,
+		205665,
+		812,
+		1,
+		1,
+		41182,
+		32,
+		212342,
+		32,
+		31220,
+		32,
+		32696,
+		32,
+		43357,
+		32,
+		32247,
+		32,
+		38314,
+		32,
+		35892428,
+		10,
+		9462713,
+		1021,
+		10,
+		38887044,
+		32947,
+		10,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0,
+		0
+  ]
+}