I had the counting inputs connected directly to a PALCE22V10, which is a high-impedance CMOS input. This input was very sensitive to noise as it appeared later on.
I had my counter input set up with a 4K7 series resistor to the base of a BC337 and a 4K7 resistor from base to ground. The emitter connected to ground and the collector connected to VCC via a 1K resistor. The junction of the collector and the 1K I used to feed the PALCE which fed a 71054 (PIT).
I could not use a capacitor in this application because I was counting pulses and because the application should be able to count at high speeds any kind of filtering would decrease the performance.
But in your case this circuit in combination with what Erik suggest could very well do the "trick". Or maybe only Erik's suggestion would be sufficiant.