diff --git a/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.C b/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.C
index 44f5fa2bfd..9c5eeb17ca 100644
--- a/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.C
+++ b/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.C
@@ -85,7 +85,7 @@ Foam::explicitPorositySource::explicitPorositySource
     porosityPtr_(NULL),
     UName_(coeffs_.lookupOrDefault<word>("UName", "U")),
     rhoName_(coeffs_.lookupOrDefault<word>("rhoName", "rho")),
-    muName_(coeffs_.lookupOrDefault<word>("muName", "mu"))
+    muName_(coeffs_.lookupOrDefault<word>("muName", "thermo:mu"))
 {
     initialise();
 }
diff --git a/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.H b/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.H
index 3048b53cae..30fc6c90da 100644
--- a/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.H
+++ b/src/fieldSources/derived/explicitPorositySource/explicitPorositySource.H
@@ -88,7 +88,8 @@ protected:
         //- Density field name (compressible case only), default = rho
         word rhoName_;
 
-        //- Dynamic viscosity field name (compressible case only), default = mu
+        //- Dynamic viscosity field name (compressible case only)
+        //  default = thermo:mu
         word muName_;