diff --git a/packages/concerto-core/lib/introspect/mapkeytype.js b/packages/concerto-core/lib/introspect/mapkeytype.js
index 5ffa2a3c0..41bd364be 100644
--- a/packages/concerto-core/lib/introspect/mapkeytype.js
+++ b/packages/concerto-core/lib/introspect/mapkeytype.js
@@ -69,22 +69,14 @@ class MapKeyType extends Decorated {
      * @protected
      */
     validate() {
-
         if (!ModelUtil.isPrimitiveType(this.type)) {
-
             const decl = this.modelFile.getType(this.ast.type.name);
-
+            // All but StringScalar & DateTimeScalar are unsupported.
             if  (!ModelUtil.isValidMapKeyScalar(decl)) {
                 throw new IllegalModelException(
                     `Scalar must be one of StringScalar, DateTimeScalar in context of MapKeyType. Invalid Scalar: ${this.type}, for MapDeclaration ${this.parent.name}`
                 );
             }
-
-            if (decl?.isConcept?.() || decl?.isClassDeclaration?.()) {
-                throw new IllegalModelException(
-                    `Invalid Map key type in MapDeclaration ${this.parent.name}. Only String and DateTime types are supported for Map key types`
-                );
-            }
         }
     }
 
@@ -95,8 +87,7 @@ class MapKeyType extends Decorated {
      * @private
      */
     processType(ast) {
-        let decl;
-        switch(this.ast.$class) {
+        switch(ast.$class) {
         case `${MetaModelNamespace}.DateTimeMapKeyType`:
             this.type = 'DateTime';
             break;
diff --git a/packages/concerto-core/lib/modelutil.js b/packages/concerto-core/lib/modelutil.js
index d83210b21..1a1978d39 100644
--- a/packages/concerto-core/lib/modelutil.js
+++ b/packages/concerto-core/lib/modelutil.js
@@ -316,9 +316,8 @@ class ModelUtil {
      * @return {boolean} true if the Key is a valid Map Key Scalar type
     */
     static isValidMapKeyScalar(decl) {
-        return (decl?.isScalarDeclaration?.() &&
-        (decl?.ast.$class !== `${MetaModelNamespace}.StringScalar`  ||
-        decl?.ast.$class !== `${MetaModelNamespace}.DateTimeScalar`));
+        return (decl?.isScalarDeclaration?.() && decl?.ast.$class === `${MetaModelNamespace}.StringScalar`)  ||
+        (decl?.isScalarDeclaration?.() && decl?.ast.$class === `${MetaModelNamespace}.DateTimeScalar`);
     }
 
     /**
diff --git a/packages/concerto-core/test/data/parser/mapdeclaration/mapdeclaration.goodkey.declaration.enum.cto b/packages/concerto-core/test/data/parser/mapdeclaration/mapdeclaration.goodkey.declaration.enum.cto
deleted file mode 100644
index b46f62cef..000000000
--- a/packages/concerto-core/test/data/parser/mapdeclaration/mapdeclaration.goodkey.declaration.enum.cto
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-namespace com.acme@1.0.0
-
-enum Phase {
-  o ONE
-  o TWO
-}
-map Dictionary {
-  o Phase
-  o String
-}
diff --git a/packages/concerto-core/test/introspect/mapdeclaration.js b/packages/concerto-core/test/introspect/mapdeclaration.js
index 49ef1af6b..aa0dc1156 100644
--- a/packages/concerto-core/test/introspect/mapdeclaration.js
+++ b/packages/concerto-core/test/introspect/mapdeclaration.js
@@ -298,36 +298,55 @@ describe('MapDeclaration', () => {
         it('should throw if ast contains illegal Map Key Type - Concept', () => {
             (() =>  {
                 let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.declaration.concept.cto', MapDeclaration);
-                decl.validate().should.throw(IllegalModelException);
-            });
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
+        });
+
+        it('should throw if ast contains illegal Map Key Type - Enum', () => {
+            (() =>  {
+                let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.declaration.enum.cto', MapDeclaration);
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
         });
 
         it('should throw if ast contains illegal Map Key Type - Scalar Long', () => {
             (() =>  {
                 let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.scalar.long.cto', MapDeclaration);
-                decl.validate();
-            });
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
         });
 
         it('should throw if ast contains illegal Map Key Type - Scalar Integer', () => {
             (() =>  {
                 let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.scalar.integer.cto', MapDeclaration);
-                decl.validate().should.throw(IllegalModelException);
-            });
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
         });
 
         it('should throw if ast contains illegal Map Key Type - Scalar Double', () => {
             (() =>  {
                 let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.scalar.double.cto', MapDeclaration);
-                decl.validate().should.throw(IllegalModelException);
-            });
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
         });
 
         it('should throw if ast contains illegal Map Key Type - Scalar Boolean', () => {
             (() =>  {
                 let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.scalar.boolean.cto', MapDeclaration);
-                decl.validate().should.throw(IllegalModelException);
-            });
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
         });
 
         it('should throw if ast contains illegal Map Key Type - Boolean', () => {
@@ -414,8 +433,10 @@ describe('MapDeclaration', () => {
                 const base_cto = fs.readFileSync('test/data/parser/mapdeclaration/base.cto', 'utf-8');
                 introspectUtils.modelManager.addCTOModel(base_cto, 'base.cto');
                 let decl = introspectUtils.loadLastDeclaration('test/data/parser/mapdeclaration/mapdeclaration.badkey.imported.thing.cto', MapDeclaration);
-                decl.validate().should.throw(IllegalModelException);
-            });
+                (() => {
+                    decl.validate();
+                }).should.throw(IllegalModelException);
+            })();
         });
     });