Invalid use of arguments! 0 expected matches, 1 entry

Although the error is rather descriptive, I could not see it. For lines:

    PowerMockito.when(
            mockStringMessageService.lookupString(Matchers.eq("XYZ")))
            .thenReturn(Matchers.eq("XYZ"));

      

        
        
        
      

    

Mistake:

[junit] Invalid use of argument matchers!
[junit] 0 matchers expected, 1 recorded:
[junit] -> at com.amazon.kilvish.types.StatusTableTest.setUp(StatusTableTest.java:61)
[junit] 
[junit] This exception may occur if matchers are combined with raw values:
[junit]     //incorrect:
[junit]     someMethod(anyObject(), "raw String");
[junit] When using matchers, all arguments have to be provided by matchers.
[junit] For example:
[junit]     //correct:
[junit]     someMethod(anyObject(), eq("String by matcher"));
[junit] 
[junit] For more info see javadoc for Matchers class.

      

        
        
        
      

    

Why are 0 matches expected?