diff --git a/src/fslsurface/Makefile b/src/fslsurface/Makefile
index 37f459c..008f443 100644
--- a/src/fslsurface/Makefile
+++ b/src/fslsurface/Makefile
@@ -57,7 +57,7 @@ fslsurfacegl.a: fslsurfacegl.o fslsurface.a
 	${AR} -r libfslsurfacegl.a fslsurfacegl.o
 fslsurface_backcompat.a: fslsurface_first.o fslsurface_dataconv.o fslsurface.a
 	${AR} -r libfslsurface_backcompat.a fslsurface_first.o fslsurface_dataconv.o
-fslsurfacemaths: fslsurface.a fslsurfacemaths.o
+fslsurfacemaths: fslsurface.a fslsurfacemaths.o fslsurfaceio.o fslsurfacefns.o fslsurface_first.o fslsurface.o
 	${CXX} ${CXXFLAGS} ${LDFLAGS} -o $@ fslsurfacemaths.o fslsurfaceio.o fslsurfacefns.o fslsurface_first.o fslsurface.o ${LIBS} ${FMLIBS}
-marching_cubes: fslsurface.a marching_cubes.o
+marching_cubes: fslsurface.a marching_cubes.o fslsurfaceio.o fslsurfacefns.o
 	${CXX} ${CXXFLAGS} ${LDFLAGS} -o $@ marching_cubes.o fslsurfaceio.o fslsurfacefns.o ${LIBS} ${FMLIBS}