diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0035c40..a1ca69f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -33,7 +33,7 @@ if (BUILD_GEOS_GTFV3_INTERFACE)
   message(STATUS "Building GEOS-gtFV3 interface")
 
   add_definitions(-DRUN_GTFV3)
-  
+
   # The Python library creation requires mpiexec/mpirun to run on a
   # compute node. Probably a weird SLURM thing?
   find_package(MPI REQUIRED)
@@ -124,6 +124,12 @@ endif ()
 if (FV_PRECISION STREQUAL R4)
    set (GFDL fms_r4)
 elseif (FV_PRECISION STREQUAL R4R8) # FV is R4 but FMS is R8
+   # We need to add_dependencies for fms_r4 because CMake doesn't know we
+   # need it for include purposes. In R4R8, we only ever link against
+   # fms_r4, so it doesn't know we need to build it.
+   # NOTE NOTE NOTE: This should *not* be included in GEOSgcm v12
+   #     because FMS is pre-built library in that case.
+   add_dependencies (${this} fms_r4)
    get_target_property (extra_incs fms_r4 INTERFACE_INCLUDE_DIRECTORIES)
    target_include_directories(${this} PRIVATE
    $<BUILD_INTERFACE:${extra_incs}>