diff --git a/hugr-core/src/hugr/validate/test.rs b/hugr-core/src/hugr/validate/test.rs
index 0da54c5fe..ec5790a75 100644
--- a/hugr-core/src/hugr/validate/test.rs
+++ b/hugr-core/src/hugr/validate/test.rs
@@ -1,3 +1,6 @@
+use std::fs::File;
+use std::io::BufReader;
+
 use cool_asserts::assert_matches;
 use rstest::rstest;
 
@@ -19,7 +22,7 @@ use crate::std_extensions::logic::test::{and_op, or_op};
 use crate::std_extensions::logic::{self, NotOp};
 use crate::types::type_param::{TypeArg, TypeArgError};
 use crate::types::{CustomType, FunctionType, PolyFuncType, Type, TypeBound, TypeRow};
-use crate::{const_extension_ids, type_row, Direction, IncomingPort, Node};
+use crate::{const_extension_ids, test_file, type_row, Direction, IncomingPort, Node};
 
 const NAT: Type = crate::extension::prelude::USIZE_T;
 
@@ -926,6 +929,13 @@ fn cfg_children_restrictions() {
     b.remove_node(exit2);
 
     // Change the types in the BasicBlock node to work on qubits instead of bits
+    b.replace_op(
+        cfg,
+        ops::CFG {
+            signature: FunctionType::new(type_row![QB_T], type_row![BOOL_T]),
+        },
+    )
+    .unwrap();
     b.replace_op(
         block,
         ops::DataflowBlock {
@@ -989,6 +999,23 @@ fn cfg_connections() -> Result<(), Box<dyn std::error::Error>> {
     Ok(())
 }
 
+#[test]
+fn cfg_entry_io_bug() -> Result<(), Box<dyn std::error::Error>> {
+    // load test file where input node of entry block has types in reversed
+    // order compared to parent CFG node.
+    let mut hugr: Hugr = serde_json::from_reader(BufReader::new(
+        File::open(test_file!("issue-1189.json")).unwrap(),
+    ))
+    .unwrap();
+    assert_matches!(
+        hugr.update_validate(&PRELUDE_REGISTRY),
+        Err(ValidationError::InvalidChildren { parent, source: ChildrenValidationError::IOSignatureMismatch{..}, .. })
+            => assert_eq!(parent, hugr.root())
+    );
+
+    Ok(())
+}
+
 #[cfg(feature = "extension_inference")]
 mod extension_tests {
     use self::ops::handle::{BasicBlockID, TailLoopID};
diff --git a/hugr-core/src/ops/validate.rs b/hugr-core/src/ops/validate.rs
index aaee46049..8f2e077fb 100644
--- a/hugr-core/src/ops/validate.rs
+++ b/hugr-core/src/ops/validate.rs
@@ -12,7 +12,7 @@ use thiserror::Error;
 
 use crate::types::TypeRow;
 
-use super::dataflow::DataflowParent;
+use super::dataflow::{DataflowOpTrait, DataflowParent};
 use super::{impl_validate_op, BasicBlock, ExitBlock, OpTag, OpTrait, OpType, ValidateOp};
 
 /// A set of property flags required for an operation.
@@ -121,9 +121,37 @@ impl ValidateOp for super::CFG {
 
     fn validate_op_children<'a>(
         &self,
-        children: impl Iterator<Item = (NodeIndex, &'a OpType)>,
+        mut children: impl Iterator<Item = (NodeIndex, &'a OpType)>,
     ) -> Result<(), ChildrenValidationError> {
-        for (child, optype) in children.dropping(2) {
+        let (entry, entry_op) = children.next().unwrap();
+        let (exit, exit_op) = children.next().unwrap();
+        let entry_op = entry_op
+            .as_dataflow_block()
+            .expect("Child check should have already checked valid ops.");
+        let exit_op = exit_op
+            .as_exit_block()
+            .expect("Child check should have already checked valid ops.");
+
+        let sig = self.signature();
+        if entry_op.inner_signature().input() != sig.input() {
+            return Err(ChildrenValidationError::IOSignatureMismatch {
+                child: entry,
+                actual: entry_op.inner_signature().input().clone(),
+                expected: sig.input().clone(),
+                node_desc: "BasicBlock Input",
+                container_desc: "CFG",
+            });
+        }
+        if &exit_op.cfg_outputs != sig.output() {
+            return Err(ChildrenValidationError::IOSignatureMismatch {
+                child: exit,
+                actual: exit_op.cfg_outputs.clone(),
+                expected: sig.output().clone(),
+                node_desc: "BasicBlockExit Output",
+                container_desc: "CFG",
+            });
+        }
+        for (child, optype) in children {
             if optype.tag() == OpTag::BasicBlockExit {
                 return Err(ChildrenValidationError::InternalExitChildren { child });
             }
diff --git a/resources/test/issue-1189.json b/resources/test/issue-1189.json
new file mode 100644
index 000000000..0b36c92dc
--- /dev/null
+++ b/resources/test/issue-1189.json
@@ -0,0 +1,136 @@
+{
+    "version": "v1",
+    "nodes": [
+        {
+            "parent": 0,
+            "op": "CFG",
+            "signature": {
+                "t": "G",
+                "input": [
+                    {
+                        "t": "Sum",
+                        "s": "Unit",
+                        "size": 1
+                    },
+                    {
+                        "t": "Sum",
+                        "s": "Unit",
+                        "size": 2
+                    }
+                ],
+                "output": [
+                    {
+                        "t": "Sum",
+                        "s": "Unit",
+                        "size": 2
+                    }
+                ],
+                "extension_reqs": []
+            }
+        },
+        {
+            "parent": 0,
+            "op": "DataflowBlock",
+            "inputs": [
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 2
+                },
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 1
+                }
+            ],
+            "other_outputs": [
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 2
+                }
+            ],
+            "sum_rows": [
+                []
+            ],
+            "extension_delta": []
+        },
+        {
+            "parent": 1,
+            "op": "Input",
+            "types": [
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 2
+                },
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 1
+                }
+            ]
+        },
+        {
+            "parent": 1,
+            "op": "Output",
+            "types": [
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 1
+                },
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 2
+                }
+            ]
+        },
+        {
+            "parent": 0,
+            "op": "ExitBlock",
+            "cfg_outputs": [
+                {
+                    "t": "Sum",
+                    "s": "Unit",
+                    "size": 2
+                }
+            ]
+        }
+    ],
+    "edges": [
+        [
+            [
+                2,
+                1
+            ],
+            [
+                3,
+                0
+            ]
+        ],
+        [
+            [
+                2,
+                0
+            ],
+            [
+                3,
+                1
+            ]
+        ],
+        [
+            [
+                1,
+                0
+            ],
+            [
+                4,
+                0
+            ]
+        ]
+    ],
+    "metadata": null,
+    "encoder": "hugr-py v0.2.1"
+}