diff --git a/cime_config/namelist_definition_mosart.xml b/cime_config/namelist_definition_mosart.xml
index d10f7d1..00b3deb 100644
--- a/cime_config/namelist_definition_mosart.xml
+++ b/cime_config/namelist_definition_mosart.xml
@@ -261,13 +261,13 @@
     <type>integer(6)</type> 
     <category>history</category>
     <group>mosart_inparm</group> 
-    <valid_values>1,2</valid_values>
+    <valid_values>1</valid_values>
     <values>
-      <value>2</value>
+      <value>1</value>
     </values>
     <desc>
       Per tape series  history file density (i.e. output precision) 
-      1=double precision, 2=single precision
+      1=double precision, 2=single precision (NOT working)
     </desc>
   </entry>
 
diff --git a/docs/ChangeLog b/docs/ChangeLog
index 240dbce..d80f761 100644
--- a/docs/ChangeLog
+++ b/docs/ChangeLog
@@ -1,9 +1,39 @@
+===============================================================
+Tag name:  release-cesm2.0.03
+Originator(s): erik
+Date: Oct 19, 2018
+One-line Summary: Remove ability to write out single-precision history because of issues
+
+Don't allow the namelist option rtmhist_ndens to be set to 2, because this
+option doesn't currently function. The simple fix we put into place for it
+is not robust.
+
+MOSART Master Tag This Corresponds To: mosart1_0_31 (with changes)
+
+Issues Fixed: #10
+  #18 -- rtmhist_ndens=2 does NOT work (so don't allow it as an option)
+
+Science  changes since: release-cesm2.0.01 
+   * None
+Software changes since: release-cesm2.0.01
+   * None
+
+Testing: Run mosart test suite
+   hobart ---- PASS
+   cheyenne -- PASS
+
+Pull Requests that document the changes (include PR ids):
+
+ #19 -- Don't allow single precision history output
+
 ===============================================================
 Tag name:  release-cesm2.0.02
 Originator(s): erik/billsacks
-Date: Oct 12, 2018
+Date: Oct 16, 2018
 One-line Summary:  Fix for py3 
 
+Fix for python3, using the floor operator for integer division.
+
 MOSART Master Tag This Corresponds To: mosart1_0_31 (with changes)
 
 Issues Fixed: #10
@@ -18,7 +48,9 @@ Pull Requests that document the changes (include PR ids):
 
  #17 -- Changes to fix #10, where an integer divide needs the floor operator
 
-Testing:
+Testing: Run mosart test suite
+   hobart ---- PASS
+   cheyenne -- PASS
 
 ===============================================================
 Tag name:  release-cesm2.0.01
@@ -34,6 +66,9 @@ is direct from jedwards4b (other than r8th addition).
 
 MOSART Master Tag This Corresponds To: mosart1_0_31 (with changes)
 
+Issues Fixed: #18
+  #18 -- rtmhist_ndens=2 does NOT work (simplest fix that converts to single on output)
+
 Science  changes since: release-cesm2.0.00
    Added in 8th degree routing file (r8th)
 Software changes since: release-cesm2.0.00
diff --git a/src/riverroute/RtmHistFile.F90 b/src/riverroute/RtmHistFile.F90
index 9f0ad69..7a3ba55 100644
--- a/src/riverroute/RtmHistFile.F90
+++ b/src/riverroute/RtmHistFile.F90
@@ -42,7 +42,7 @@ module RtmHistFile
 !
   integer :: ni
   integer, public :: &
-       rtmhist_ndens(max_tapes) = 2         ! namelist: output density of netcdf history files
+       rtmhist_ndens(max_tapes) = 1         ! namelist: output density of netcdf history files
   integer, public :: &
        rtmhist_mfilt(max_tapes) = 30        ! namelist: number of time samples per tape
   integer, public :: &
diff --git a/src/riverroute/RtmIO.F90 b/src/riverroute/RtmIO.F90
index 6bfae8c..18be51b 100644
--- a/src/riverroute/RtmIO.F90
+++ b/src/riverroute/RtmIO.F90
@@ -1827,7 +1827,7 @@ subroutine ncd_io_real_var1(varname, data, dim1name, &
           call pio_setframe(ncid,vardesc, int(nt,kind=PIO_Offset_kind))
        end if
        if(xtype == ncd_float) then
-          call pio_write_darray(ncid, vardesc, iodesc_plus%iodesc, real(data, kind=r4), status, fillval=real(spval,kind=r4))
+          call shr_sys_abort( subname//' error: Attempt to write out single-precision data which is current NOT implemented (see issue #18)' )
        else
           call pio_write_darray(ncid, vardesc, iodesc_plus%iodesc, data, status, fillval=spval)
        endif