diff --git a/samples/f90/Makefile.in b/samples/f90/Makefile.in
index da79d7126..6086ff57a 100644
--- a/samples/f90/Makefile.in
+++ b/samples/f90/Makefile.in
@@ -3,7 +3,6 @@ include ../Cantera.mak
 F90=@F90@
 RM=rm -f
 F90FLAGS=-g
-FORTRANMODDIRPREFIX=@FORTRANMODDIRPREFIX@
 F90MODDIR=$(CANTERA_FORTRAN_MODS)
 LDFLAGS=
 LDLIBS=$(CANTERA_FORTRAN_LIBS)
@@ -17,7 +16,7 @@ all: @make_target@
 	$(F90) $(LDFLAGS) -o @make_target@ $(OBJS) $(LDLIBS)
 
 %.o : %.f90
-	$(F90) -c $< $(FORTRANMODDIRPREFIX)$(F90MODDIR) $(F90FLAGS)
+	$(F90) -c $< @FORTRANMODDIRPREFIX@$(F90MODDIR) $(F90FLAGS)
 
 clean:
 	$(RM) $(OBJS)