Why is my class abstract? It's override seems to have same signature?

I am working on a project which has a class inheritance scheme like this:

Drive
    |
    v
FileDrive
    |
    v
StreamDrive
    |
    v
BufferStreamDrive_base
    |
    v
BufferStreamDrive

In Drive there is a virtual method declared like this:

virtual Drive::Type GetDriveType(void) const = 0;

Then in FileDrive it is overridden with this:

virtual Drive::Type GetDriveType(void) const;

with the following implementation:

Drive::Type
FileDrive::GetDriveType(void) const
{
    return Drive::FILEDRIVE;
}

However, when I compile the code I get an error like this:

libtool: compile:  x86_64-w64-mingw32.shared-g++ -DHAVE_CONFIG_H -I. -I../../include -I../../include -I./../../include -I./../../libraries/libmbc -I./../../libraries/libmbutil -I./../../libraries/libmbmath -I./../../libraries/libmbwrap -I./../../libraries/libann -I./../../mbdyn -I./../../mbdyn/base -I./../../mbdyn/struct -I./../../mbdyn/aero -I./../../mbdyn/elec -I./../../mbdyn/thermo -I./../../mbdyn/hydr -I./../../modules -I/opt/mxe/usr/x86_64-w64-mingw32.static/include/suitesparse -std=c++11 -D_USE_MATH_DEFINES -pthread -MT constltp_impl.lo -MD -MP -MF .deps/constltp_impl.Tpo -c constltp_impl.cc  -DDLL_EXPORT -DPIC -o .libs/constltp_impl.o
In file included from dataman.h:43:0,
                 from bufferstreamdrive.cc:36:
bufferstreamdrive.cc: In function 'Drive* ReadBufferStreamDrive(const DataManager*, MBDynParser&, unsigned int)':
bufferstreamdrive.cc:291:21: error: invalid new-expression of abstract class type 'BufferStreamDrive'
     InputEvery, pSDE));
                     ^
./../../libraries/libmbutil/mynewmem.h:658:14: note: in definition of macro 'SAFENEWWITHCONSTRUCTOR_'
  (pnt) = new constructor
              ^
bufferstreamdrive.cc:287:3: note: in expansion of macro 'SAFENEWWITHCONSTRUCTOR'
   SAFENEWWITHCONSTRUCTOR(pDr, BufferStreamDrive,
   ^
In file included from bufferstreamdrive.cc:39:0:
bufferstreamdrive.h:68:7: note:   because the following virtual functions are pure within 'BufferStreamDrive':
 class BufferStreamDrive : public BufferStreamDrive_base {
       ^
In file included from tpldrive.h:35:0,
                 from rbk.h:38,
                 from reffrm.h:44,
                 from mbpar.h:110,
                 from dataman.h:47,
                 from bufferstreamdrive.cc:36:
drive.h:117:22: note:   virtual Drive::Type Drive::GetDriveType() const
  virtual Drive::Type GetDriveType(void) const = 0;
                      ^

What is the problem here? I can't see it.