diff --git a/tests/baz/1.0/IBase.hal b/tests/baz/1.0/IBase.hal
index add4153..7f90f16 100644
--- a/tests/baz/1.0/IBase.hal
+++ b/tests/baz/1.0/IBase.hal
@@ -17,7 +17,7 @@
 package android.hardware.tests.baz@1.0;
 
 interface IBase {
-    enum SomeBaseEnum {
+    enum SomeBaseEnum : int32_t {
         grrr = 1,
     };
 
diff --git a/tests/expression/1.0/IExpression.hal b/tests/expression/1.0/IExpression.hal
index a44e03c..6eb5b2a 100644
--- a/tests/expression/1.0/IExpression.hal
+++ b/tests/expression/1.0/IExpression.hal
@@ -178,7 +178,7 @@
     MAX_PLUS_2 // 1
   };
 
-  enum Constants {
+  enum Constants : int32_t {
     CONST_FOO,
     CONST_BAR = 70,
     MAX_ARRAY_SIZE = 20,