diff --git a/internal/engine/dolphin/convert.go b/internal/engine/dolphin/convert.go
index cfd83b5c4d..6c761802e4 100644
--- a/internal/engine/dolphin/convert.go
+++ b/internal/engine/dolphin/convert.go
@@ -1556,6 +1556,12 @@ func (c *cc) convertTruncateTableStmt(n *pcast.TruncateTableStmt) *ast.TruncateS
 }
 
 func (c *cc) convertUnaryOperationExpr(n *pcast.UnaryOperationExpr) ast.Node {
+	if n.Op == opcode.Not || n.Op == opcode.Not2 {
+		return &ast.BoolExpr{
+			Boolop: ast.BoolExprTypeNot,
+			Args:   &ast.List{Items: []ast.Node{c.convert(n.V)}},
+		}
+	}
 	return todo(n)
 }
 
diff --git a/internal/engine/dolphin/convert_test.go b/internal/engine/dolphin/convert_test.go
new file mode 100644
index 0000000000..8c552023bc
--- /dev/null
+++ b/internal/engine/dolphin/convert_test.go
@@ -0,0 +1,74 @@
+package dolphin
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/sqlc-dev/sqlc/internal/sql/ast"
+	"github.com/sqlc-dev/sqlc/internal/sql/astutils"
+)
+
+// walkStmts collects every node reachable from the parsed statements.
+func walkStmts(t *testing.T, query string) []ast.Node {
+	t.Helper()
+
+	p := NewParser()
+	stmts, err := p.Parse(strings.NewReader(query))
+	if err != nil {
+		t.Fatalf("parse %q: %v", query, err)
+	}
+
+	var nodes []ast.Node
+	for i := range stmts {
+		astutils.Walk(astutils.VisitorFunc(func(n ast.Node) {
+			nodes = append(nodes, n)
+		}), stmts[i].Raw.Stmt)
+	}
+	return nodes
+}
+
+func TestConvertUnaryExpr_Not(t *testing.T) {
+	for _, tc := range []struct {
+		name  string
+		query string
+	}{
+		{
+			name:  "NOT keyword",
+			query: "SELECT personid FROM persons WHERE NOT sqlc.arg('foo')",
+		},
+		{
+			name:  "bang operator",
+			query: "SELECT personid FROM persons WHERE ! sqlc.arg('foo')",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			nodes := walkStmts(t, tc.query)
+
+			var (
+				foundNot bool
+				foundArg bool
+			)
+			for _, n := range nodes {
+				switch v := n.(type) {
+				case *ast.TODO:
+					t.Fatalf("query produced an opaque TODO node, sqlc.arg() would not be rewritten")
+				case *ast.BoolExpr:
+					if v.Boolop == ast.BoolExprTypeNot {
+						foundNot = true
+					}
+				case *ast.FuncCall:
+					if v.Func != nil && v.Func.Schema == "sqlc" && v.Func.Name == "arg" {
+						foundArg = true
+					}
+				}
+			}
+
+			if !foundNot {
+				t.Errorf("expected a BoolExpr with BoolExprTypeNot in the AST")
+			}
+			if !foundArg {
+				t.Errorf("expected the nested sqlc.arg() FuncCall to be reachable in the AST")
+			}
+		})
+	}
+}