diff --git a/CHANGELOG.md b/CHANGELOG.md
index d6cb1481647..ce79321801f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,10 @@ release.
 
 ### Context
 
+- Clarify that environment variable propagation carriers normalize requested
+  keys, carrier keys, and returned keys.
+  ([#5102](https://github.com/open-telemetry/opentelemetry-specification/pull/5102))
+
 ### Traces
 
 ### Metrics
diff --git a/specification/context/env-carriers.md b/specification/context/env-carriers.md
index c388496c158..4d730e43aa5 100644
--- a/specification/context/env-carriers.md
+++ b/specification/context/env-carriers.md
@@ -66,6 +66,21 @@ Environment variable names used for context propagation:
     (`_`) with an underscore (`_`),
   - prefixing the name with an underscore (`_`) if it would otherwise start with
     an ASCII digit.
+- MUST be normalized consistently by `Get`, `Set`, and `Keys` operations:
+  - when injecting context, the carrier `Set` operation MUST write values using
+    the normalized form of the key provided by the propagator,
+  - when extracting context, the carrier `Get` operation MUST normalize the key
+    requested by the propagator and the key names present in the carrier before
+    matching them. If multiple carrier key names normalize to the same key name,
+    the carrier is ambiguous and in that case, the value returned by `Get` is
+    unspecified,
+  - when listing keys, the carrier `Keys` function MUST return normalized key
+    names.
+
+For example, if a propagator requests the key `x-b3-traceid`, the environment
+variable carrier MUST match it to the carrier key `X_B3_TRACEID`. It MUST also
+match it to a carrier key such as `x-b3-traceid`, because both key names
+normalize to `X_B3_TRACEID`.
 
 > [!NOTE]
 > This normalization is consistent with the environment variable naming rules