diff --git a/content/master/concepts/environment-configs.md b/content/master/concepts/environment-configs.md
index 74dc3f13f..a16724f15 100644
--- a/content/master/concepts/environment-configs.md
+++ b/content/master/concepts/environment-configs.md
@@ -196,16 +196,76 @@ spec:
     - type: Selector
       selector: 
         matchLabels:
-          - key: my-label-key
+          - key: my-first-label-key
             type: Value
-            value: my-label-value
-          - key: my-label-key
+            value: my-first-label-value
+          - key: my-second-label-key
             type: FromCompositeFieldPath
             valueFromFieldPath: spec.parameters.deploy
   resources:
   # Removed for brevity
 ```
 
+By default, Crossplane errors out if a
+{{<hover label="byLabel" line="16">}}valueFromFieldPath{{</hover>}}
+field doesn't exist in the composite resource at runtime. You can change this
+behavior by setting the
+{{<hover label="byLabelOptional" line="17">}}fromFieldPathPolicy{{</hover>}}
+field to `Optional`, resulting in the key being ignored if not found instead.
+
+```yaml {label="byLabelOptional",copy-lines="all"}
+apiVersion: apiextensions.crossplane.io/v1
+kind: Composition
+metadata:
+  name: example-composition
+spec:
+  environment:
+    environmentConfigs:
+      - type: Selector
+        selector:
+          matchLabels:
+            - key: my-first-label-key
+              type: Value
+              value: my-first-label-value
+            - key: my-second-label-key
+              type: FromCompositeFieldPath
+              valueFromFieldPath: spec.parameters.deploy
+              fromFieldPathPolicy: Optional
+  resources:
+  # Removed for brevity
+```
+
+Label selectors are evaluated in order, so if a label set as optional is not
+found, but an explicit value for it was defined already, the
+{{<hover label="byLabelOptionalDefault" line="16">}}default value{{</hover>}}
+is used instead.
+
+```yaml {label="byLabelOptionalDefault",copy-lines="all"}
+apiVersion: apiextensions.crossplane.io/v1
+kind: Composition
+metadata:
+  name: example-composition
+spec:
+  environment:
+    environmentConfigs:
+      - type: Selector
+        selector:
+          matchLabels:
+            - key: my-first-label-key
+              type: Value
+              value: my-label-value
+            - key: my-second-label-key
+              type: Value
+              value: my-default-value
+            - key: my-second-label-key
+              type: FromCompositeFieldPath
+              valueFromFieldPath: spec.parameters.deploy
+              fromFieldPathPolicy: Optional
+  resources:
+  # Removed for brevity
+```
+
+
 #### Manage selector results
 
 Selecting environments by labels may return more than one environment.