diff --git a/src/visitor.ts b/src/visitor.ts
index 669abaa..06162a5 100644
--- a/src/visitor.ts
+++ b/src/visitor.ts
@@ -376,12 +376,12 @@ export class Visitor{
 				this.where += ")";
 				break;
 			case "tolower":
-				this.where += "LCASE(";
+				this.where += this.type === SQLLang.MsSql ? "LOWER(" : "LCASE(";
 				this.Visit(params[0], context);
 				this.where += ")";
 				break;
 			case "toupper":
-				this.where += "UCASE(";
+				this.where += this.type === SQLLang.MsSql ? "UPPER(" :"UCASE(";
 				this.Visit(params[0], context);
 				this.where += ")";
 				break;
diff --git a/test/mssql.spec.js b/test/mssql.spec.js
index 3077afd..661ab16 100644
--- a/test/mssql.spec.js
+++ b/test/mssql.spec.js
@@ -109,11 +109,11 @@ describe("SQL WHERE useParameters (MS-SQL)", () => {
   })
 
   it("expression 5.1.1.4.7: tolower(A) eq 'abc'", () => {
-      expect(f.where).to.equal("LCASE([A]) = @p0")
+      expect(f.where).to.equal("LOWER([A]) = @p0")
   })
 
   it("expression 5.1.1.4.8: toupper(A) eq 'ABC'", () => {
-      expect(f.where).to.equal("UCASE([A]) = @p0")
+      expect(f.where).to.equal("UPPER([A]) = @p0")
   })
 
   it("expression 5.1.1.4.9: trim(A) eq 'abc'", () => {