diff --git a/compatibility_matrices/compatibility_matrix.4.xml b/compatibility_matrices/compatibility_matrix.4.xml
index 8ef0b3a..b9fb3f4 100644
--- a/compatibility_matrices/compatibility_matrix.4.xml
+++ b/compatibility_matrices/compatibility_matrix.4.xml
@@ -7,7 +7,7 @@
             <instance>default</instance>
         </interface>
     </hal>
-    <hal format="hidl" optional="false">
+    <hal format="hidl" optional="true">
         <name>android.hardware.audio</name>
         <version>5.0</version>
         <interface>
@@ -15,7 +15,7 @@
             <instance>default</instance>
         </interface>
     </hal>
-    <hal format="hidl" optional="false">
+    <hal format="hidl" optional="true">
         <name>android.hardware.audio.effect</name>
         <version>5.0</version>
         <interface>
@@ -171,7 +171,7 @@
             <instance>default</instance>
         </interface>
     </hal>
-    <hal format="hidl" optional="false">
+    <hal format="hidl" optional="true">
         <name>android.hardware.gatekeeper</name>
         <version>1.0</version>
         <interface>
@@ -199,7 +199,7 @@
             <instance>default</instance>
         </interface>
     </hal>
-    <hal format="hidl" optional="false">
+    <hal format="hidl" optional="true">
         <name>android.hardware.graphics.composer</name>
         <version>2.1-3</version>
         <interface>
@@ -207,7 +207,7 @@
             <instance>default</instance>
         </interface>
     </hal>
-    <hal format="hidl" optional="false">
+    <hal format="hidl" optional="true">
         <name>android.hardware.graphics.mapper</name>
         <version>2.1</version>
         <version>3.0</version>