diff --git a/compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/semantics/analyzer/Types.java b/compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/semantics/analyzer/Types.java
index 62b4245979f5..c378ef68914c 100644
--- a/compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/semantics/analyzer/Types.java
+++ b/compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/semantics/analyzer/Types.java
@@ -1478,6 +1478,7 @@ private boolean isFunctionTypeAssignable(BInvokableType source, BInvokableType t
     }
 
     private boolean isTypeParamAssignable(BType sourceParam, BType targetParam) {
+        // xml is special cased due to this issue: https://github.com/ballerina-platform/ballerina-spec/issues/1319
         return isAssignable(sourceParam, targetParam) ||
                 (isAssignable(sourceParam, symTable.xmlType) && isAssignable(targetParam, sourceParam));
     }