diff --git a/packages/aws-cdk-lib/aws-ec2/lib/instance-types.ts b/packages/aws-cdk-lib/aws-ec2/lib/instance-types.ts
index 53bf6b7fb32fd..0c2c36d1b18a7 100644
--- a/packages/aws-cdk-lib/aws-ec2/lib/instance-types.ts
+++ b/packages/aws-cdk-lib/aws-ec2/lib/instance-types.ts
@@ -1414,7 +1414,7 @@ export class InstanceType {
   }
 
   public sameInstanceClassAs(other: InstanceType): boolean {
-    const instanceClass: RegExp = /^([a-z]+\d{1,2}[a-z]*)\.([a-z0-9]+)$/;
+    const instanceClass: RegExp = /^([a-z-]+\d{1,2}[a-z-]*)\.([a-z0-9-]+)$/;
     const instanceClassId = this.instanceTypeIdentifier.match(instanceClass);
     const otherInstanceClassId = other.instanceTypeIdentifier.match(instanceClass);
     if (instanceClassId == null || otherInstanceClassId == null) {
diff --git a/packages/aws-cdk-lib/aws-ec2/test/instance.test.ts b/packages/aws-cdk-lib/aws-ec2/test/instance.test.ts
index 3dcde47e3b5a8..f656ec0c3553d 100644
--- a/packages/aws-cdk-lib/aws-ec2/test/instance.test.ts
+++ b/packages/aws-cdk-lib/aws-ec2/test/instance.test.ts
@@ -679,6 +679,15 @@ test('sameInstanceClassAs compares identical InstanceTypes correctly', () => {
   expect(sameInstanceType.sameInstanceClassAs(comparitor)).toBeTruthy();
 });
 
+test('sameInstanceClassAs compares identical InstanceTypes correctly', () => {
+  // GIVEN
+  const comparitor = InstanceType.of(InstanceClass.M7I_FLEX, InstanceSize.LARGE);
+  //WHEN
+  const instanceType = new InstanceType('m7i-flex.large');
+  //THEN
+  expect(instanceType.sameInstanceClassAs(comparitor)).toBeTruthy();
+});
+
 test('sameInstanceClassAs compares InstanceTypes correctly regardless of size', () => {
   // GIVEN
   const comparitor = InstanceType.of(InstanceClass.T3, InstanceSize.LARGE);