diff --git a/src/constitutive.f90 b/src/constitutive.f90
index e627fa80c..77054dda3 100644
--- a/src/constitutive.f90
+++ b/src/constitutive.f90
@@ -151,7 +151,7 @@ subroutine constitutive_init
           write(FILEUNIT,'(a)') '(plasticity)'//char(9)//trim(outputName)
           if (phase_plasticity(ph) /= PLASTICITY_NONE_ID) then
             OutputPlasticityLoop: do o = 1,size(thisOutput(:,ins))
-              if(len(trim(thisOutput(o,ins))) > 0) &
+              if(len_trim(thisOutput(o,ins)) > 0) &
                 write(FILEUNIT,'(a,i4)') trim(thisOutput(o,ins))//char(9),thisSize(o,ins)
             enddo OutputPlasticityLoop
           endif
@@ -196,7 +196,7 @@ subroutine constitutive_init
           if (knownSource) then
             write(FILEUNIT,'(a)') '(source)'//char(9)//trim(outputName)
             OutputSourceLoop: do o = 1,size(thisOutput(:,ins))
-              if(len(trim(thisOutput(o,ins))) > 0) &
+              if(len_trim(thisOutput(o,ins)) > 0) &
                 write(FILEUNIT,'(a,i4)') trim(thisOutput(o,ins))//char(9),thisSize(o,ins)
             enddo OutputSourceLoop
           endif