diff --git a/datafusion/optimizer/src/type_coercion.rs b/datafusion/optimizer/src/type_coercion.rs
index 3ea5c63997858..018e0b9fc5e21 100644
--- a/datafusion/optimizer/src/type_coercion.rs
+++ b/datafusion/optimizer/src/type_coercion.rs
@@ -172,18 +172,19 @@ pub fn coerce_arguments_for_signature(
 mod test {
     use crate::type_coercion::TypeCoercion;
     use crate::{OptimizerConfig, OptimizerRule};
+    use arrow::datatypes::DataType;
     use datafusion_common::{DFSchema, Result};
     use datafusion_expr::logical_plan::{EmptyRelation, Projection};
-    use datafusion_expr::{lit, LogicalPlan};
+    use datafusion_expr::{
+        lit, Expr, LogicalPlan, ReturnTypeFunction, ScalarFunctionImplementation,
+        ScalarUDF, Signature, Volatility,
+    };
     use std::sync::Arc;
 
     #[test]
-    fn simple_case() -> Result<()> {
+    fn binary_expr_simple_case() -> Result<()> {
         let expr = lit(1.2_f64).lt(lit(2_u32));
-        let empty = Arc::new(LogicalPlan::EmptyRelation(EmptyRelation {
-            produce_one_row: false,
-            schema: Arc::new(DFSchema::empty()),
-        }));
+        let empty = empty();
         let plan = LogicalPlan::Projection(Projection::try_new(vec![expr], empty, None)?);
         let rule = TypeCoercion::new();
         let mut config = OptimizerConfig::default();
@@ -196,12 +197,9 @@ mod test {
     }
 
     #[test]
-    fn nested_case() -> Result<()> {
+    fn binary_expr_nested_case() -> Result<()> {
         let expr = lit(1.2_f64).lt(lit(2_u32));
-        let empty = Arc::new(LogicalPlan::EmptyRelation(EmptyRelation {
-            produce_one_row: false,
-            schema: Arc::new(DFSchema::empty()),
-        }));
+        let empty = empty();
         let plan = LogicalPlan::Projection(Projection::try_new(
             vec![expr.clone().or(expr)],
             empty,
@@ -214,4 +212,38 @@ mod test {
             \n  EmptyRelation", &format!("{:?}", plan));
         Ok(())
     }
+
+    #[test]
+    fn scalar_udf() -> Result<()> {
+        let empty = empty();
+        let return_type: ReturnTypeFunction =
+            Arc::new(move |_| Ok(Arc::new(DataType::Utf8)));
+        let fun: ScalarFunctionImplementation = Arc::new(move |_| unimplemented!());
+        let udf = Expr::ScalarUDF {
+            fun: Arc::new(ScalarUDF::new(
+                "TestScalarUDF",
+                &Signature::uniform(1, vec![DataType::Float32], Volatility::Stable),
+                &return_type,
+                &fun,
+            )),
+            args: vec![lit(123_i32)],
+        };
+        let plan = LogicalPlan::Projection(Projection::try_new(vec![udf], empty, None)?);
+        let rule = TypeCoercion::new();
+        let mut config = OptimizerConfig::default();
+        let plan = rule.optimize(&plan, &mut config)?;
+        assert_eq!(
+            "Projection: TestScalarUDF(CAST(Int32(123) AS Float32))\n  EmptyRelation",
+            &format!("{:?}", plan)
+        );
+        Ok(())
+    }
+
+    fn empty() -> Arc<LogicalPlan> {
+        let empty = Arc::new(LogicalPlan::EmptyRelation(EmptyRelation {
+            produce_one_row: false,
+            schema: Arc::new(DFSchema::empty()),
+        }));
+        empty
+    }
 }