diff --git a/cime_config/config_component.xml b/cime_config/config_component.xml
index 0decd3f0..f18e1860 100644
--- a/cime_config/config_component.xml
+++ b/cime_config/config_component.xml
@@ -304,9 +304,9 @@
 
   <entry id="CAM_LINKED_LIBS">
     <type>char</type>
-    <valid_values>-lmpas</valid_values>
+    <valid_values></valid_values>
     <default_value>-lmusica -ljsonfortran</default_value>
-    <values match="last">
+    <values match="last" modifier="additive">
       <!-- Turn off for physics testbed -->
       <value compset="_CAM%PHYSTEST"></value>
       <value grid="a%mpasa[0-9]+">-lmpas</value>