diff --git a/lib/core/src/Cardano/Wallet/Api/Types.hs b/lib/core/src/Cardano/Wallet/Api/Types.hs
index ef49280715f..0aa8cc280b4 100644
--- a/lib/core/src/Cardano/Wallet/Api/Types.hs
+++ b/lib/core/src/Cardano/Wallet/Api/Types.hs
@@ -3483,11 +3483,11 @@ instance EncodeAddress n => ToJSON (ApiMintBurnOperation n) where
 
 instance DecodeAddress n => FromJSON (ApiMintBurnOperation n) where
     parseJSON = Aeson.withObject "ApiMintBurnOperation" $ \o ->
-        case HM.toList o of
-            [("mint", mint)] -> ApiMint <$> parseJSON mint
-            [("burn", burn)] -> ApiBurn <$> parseJSON burn
-            [] -> fail "Must include a mint or burn operation"
-            _ -> fail "Each operation may be either a \"mint\" or a \"burn\"."
+        case HM.keys o of
+            ["mint"] -> ApiMint <$> o .: "mint"
+            ["burn"] -> ApiBurn <$> o .: "burn"
+            [] -> fail "Must include a \"mint\" or \"burn\" property."
+            _ -> fail "May be either a \"mint\" or a \"burn\"."
 
 instance FromJSON ApiMintedBurnedInfo where
     parseJSON = genericParseJSON defaultRecordTypeOptions
diff --git a/lib/core/test/unit/Cardano/Wallet/Api/Malformed.hs b/lib/core/test/unit/Cardano/Wallet/Api/Malformed.hs
index 17cff0cedb7..3651ce64f14 100644
--- a/lib/core/test/unit/Cardano/Wallet/Api/Malformed.hs
+++ b/lib/core/test/unit/Cardano/Wallet/Api/Malformed.hs
@@ -2064,7 +2064,7 @@ instance Malformed (BodyParam (PostMintBurnAssetData ('Testnet pm))) where
                                                                       }
                                                           }
                                                }
-                                               
+
                                }]
                 , "passphrase": #{nameTooLong}
                 }|]
@@ -2091,7 +2091,7 @@ instance Malformed (BodyParam (PostMintBurnAssetData ('Testnet pm))) where
                                                                      }
                                                          }
                                                }
-                                               
+
                                }]
                 , "passphrase": #{nameTooLong}
                 }|]
@@ -2109,11 +2109,11 @@ instance Malformed (BodyParam (PostMintBurnAssetData ('Testnet pm))) where
                                                                      }
                                                          }
                                                }
-                                               
+
                                }]
                 , "passphrase": #{nameTooLong}
                 }|]
-              , "Error in $['mint_burn'][0].operation: Each operation may either be a mint or a burn, not both"
+              , "Error in $['mint_burn'][0].operation: May be either a 'mint' or a 'burn'."
               )
             , ( [aesonQQ|
                 { "mint_burn": [{ "monetary_policy_index": "0"
@@ -2126,6 +2126,15 @@ instance Malformed (BodyParam (PostMintBurnAssetData ('Testnet pm))) where
                                }]
                 , "passphrase": ""
                 }|]
-              , "Error in $['mint_burn'][0].operation: Encountered unexpected key(s): ['something_else']"
+              , "Error in $['mint_burn'][0].operation: May be either a 'mint' or a 'burn'."
+              )
+            , ( [aesonQQ|
+                { "mint_burn": [{ "monetary_policy_index": "0"
+                                , "asset_name": "deadbeef"
+                                , "operation": {}
+                               }]
+                , "passphrase": ""
+                }|]
+              , "Error in $['mint_burn'][0].operation: Must include a 'mint' or 'burn' property."
               )
             ]