diff --git a/simulator/model/mod.rs b/simulator/model/mod.rs
index 9f125a15b..a2120cd63 100644
--- a/simulator/model/mod.rs
+++ b/simulator/model/mod.rs
@@ -561,8 +561,6 @@ impl Shadow for AlterTable {
                 });
             }
             AlterTableType::AlterColumn { old, new } => {
-                // TODO: have to see correct behaviour with indexes to see if we should error out
-                // in case there is some sort of conflict with this change
                 let col = table.columns.iter_mut().find(|c| c.name == *old).unwrap();
                 *col = new.clone();
             }
diff --git a/simulator/shrink/plan.rs b/simulator/shrink/plan.rs
index 6da5d93e8..9f80f78cc 100644
--- a/simulator/shrink/plan.rs
+++ b/simulator/shrink/plan.rs
@@ -120,6 +120,8 @@ impl InteractionPlan {
                             | Property::DeleteSelect { queries, .. }
                             | Property::DropSelect { queries, .. }
                             | Property::Queries { queries } => {
+                                // Remove placeholder queries
+                                queries.retain(|query| !matches!(query, Query::Placeholder));
                                 extensional_queries.append(queries);
                             }
                             Property::AllTableHaveExpectedContent { tables } => {
diff --git a/sql_generation/generation/query.rs b/sql_generation/generation/query.rs
index a21a37231..17fe0f843 100644
--- a/sql_generation/generation/query.rs
+++ b/sql_generation/generation/query.rs
@@ -456,7 +456,31 @@ impl ArbitraryFrom<(&Table, &[AlterTableTypeDiscriminants])> for AlterTableType
                 column: Column::arbitrary(rng, context),
             },
             AlterTableTypeDiscriminants::AlterColumn => {
-                todo!();
+                let col_diff = get_column_diff(table);
+
+                if col_diff.is_empty() {
+                    // Generate a DropColumn if we can drop a column
+                    return AlterTableType::arbitrary_from(
+                        rng,
+                        context,
+                        (
+                            table,
+                            if choices.contains(&AlterTableTypeDiscriminants::DropColumn) {
+                                ALTER_TABLE_NO_ALTER_COL
+                            } else {
+                                ALTER_TABLE_NO_ALTER_COL_NO_DROP
+                            },
+                        ),
+                    );
+                }
+
+                let col_idx = pick_index(col_diff.len(), rng);
+                let col_name = col_diff.get_index(col_idx).unwrap();
+
+                AlterTableType::AlterColumn {
+                    old: col_name.to_string(),
+                    new: Column::arbitrary(rng, context),
+                }
             }
             AlterTableTypeDiscriminants::RenameColumn => AlterTableType::RenameColumn {
                 old: pick(&table.columns, rng).name.clone(),
@@ -501,8 +525,7 @@ impl Arbitrary for AlterTable {
         ) {
             (true, true) => ALTER_TABLE_ALL,
             (true, false) => ALTER_TABLE_NO_ALTER_COL,
-            (false, true) => ALTER_TABLE_NO_DROP,
-            (false, false) => ALTER_TABLE_NO_ALTER_COL_NO_DROP,
+            (false, true) | (false, false) => ALTER_TABLE_NO_ALTER_COL_NO_DROP,
         };
 
         let alter_table_type = AlterTableType::arbitrary_from(rng, context, (table, choices));