diff --git AmberTools/src/chamber/psf_strings.F90 AmberTools/src/chamber/psf_strings.F90
index e648f73..d82ca3e 100644
--- AmberTools/src/chamber/psf_strings.F90
+++ AmberTools/src/chamber/psf_strings.F90
@@ -99,7 +99,7 @@ subroutine next_word(l,lw,ll,word)
    !on a line. The following is a hack to deal with this.
    !--- Begin hack ---
    if (ll == 1) then
-      if (l(1:1) /= " ") then
+      if (l(1:1) > " ") then
          lw = 1
          word(1:1)=l(1:1)
          l = ""
@@ -120,7 +120,7 @@ subroutine next_word(l,lw,ll,word)
    ll=ll-i+1
  !--- fill in next word ---------------------
    i=1
-   do while(i < ll .and. l(i:i) /= " ")
+   do while(i < ll .and. l(i:i) > " ")
       i=i+1
    enddo
    if(i > 1 .and. i < ll ) then
@@ -151,7 +151,7 @@ subroutine next_word(l,lw,ll,word)
    endif
  !--- remove leading blanks ----------------
    i=1
-   do while(i < ll .and. l(i:i) == " ")
+   do while(i < ll .and. l(i:i) <= " ")
       i=i+1
    enddo
    tmp_l = l