Combined heating and capacitive seat occupant sensing system, comprising a heating element for producing heat when an electrical current is caused to flow across it; a capacitive sensing circuit connected to said heating element so as to be able to use said heating element as an antenna electrode, said capacitive sensing circuit configured for driving a first alternating current at a first frequency into said heating element, said capacitive sensing circuit including a decision unit for deciding whether a seat occupant is present or not and for producing an output signal indicative of the decision; and a common mode choke connected to the terminals of said heating element for DC-coupling said heating element to a heating current supply and for suppressing alternating current flow between said heating element and said heating current supply; wherein said capacitive sensing circuit is configured for driving a second alternating current at a second frequency into said heating element, said first and second frequencies, hereinafter referred to as f 1 and f 2, respectively, are comprised in the range from 50 kHz to 10 MHz, with f 1 and f 2 spaced from each other by at least 10 kHz, said common mode choke is configured so as to satisfy at least one of the following conditions: a) -5% ≤ [K REAL (f 1, f 2, T)-K REAL (f 1, f 2, T REF)]/K REAL (f 1, f 2, T REF) ≤ 5%, for any temperature T in the range from -40°C to +150°C, where T REF = 25°C and where the function K REAL (f x, f y, T) is defined as the ratio G(f y, T)/G(f x, T), where G(f x, T) and G(f y, T) is the conductance, at temperature T, of the common mode choke at a frequency f x and f y, respectively; b) -3% ≤ [K IMAG (f 1, f 2, T)-K IMAG (f 1, f 2, T REF)]/K IMAG (f 1, f 2, T REF) ≤ 3%, for any temperature T in the range from -40°C to +150°C, where T REF = 25°C and where the function K IMAG (f x, f y, T) is defined as the ratio L(f y, T)/L(f x, T), where L(f x, T) and L(f y, T) is the inductance, at temperature T, of the common mode choke at a frequency f x and f y, respectively; c) -20% ≤ [ΔL(f 1, f 2, T)-ΔL(f 1, f 2, T REF)]/ΔL(f 1, f 2, T REF) ≤ 20%, for any temperature T in the range from -40°C to +150°C, where T REF = 25°C and where the function ΔL(f x, f y, T) is defined as the difference L(f y, T)-L(f x, T), where L(f x, T) and L(f y, T) is the inductance, at a temperature T, of the common mode choke at a frequency f x and f y, respectively; and said decision unit is configured for deciding whether a seat occupant is present or not based upon said first and second alternating currents while taking into account the condition a), b) or c) satisfied by said common mode choke in such a way as to compensate an influence of common mode choke temperature on said decision. a) -5% ≤ [K REAL (f 1, f 2, T)-K REAL (f 1, f 2, T REF)]/K REAL (f 1, f 2, T REF) ≤ 5%, for any temperature T in the range from -40°C to +150°C, where T REF = 25°C and where the function K REAL (f x, f y, T) is defined as the ratio G(f y, T)/G(f x, T), where G(f x, T) and G(f y, T) is the conductance, at temperature T, of the common mode choke at a frequency f x and f y, respectively; b) -3% ≤ [K IMAG (f 1, f 2, T)-K IMAG (f 1, f 2, T REF)]/K IMAG (f 1, f 2, T REF) ≤ 3%, for any temperature T in the range from -40°C to +150°C, where T REF = 25°C and where the function K IMAG (f x, f y, T) is defined as the ratio L(f y, T)/L(f x, T), where L(f x, T) and L(f y, T) is the inductance, at temperature T, of the common mode choke at a frequency f x and f y, respectively; c) -20% ≤ [ΔL(f 1, f 2, T)-ΔL(f 1, f 2, T REF)]/ΔL(f 1, f 2, T REF) ≤ 20%, for any temperature T in the range from -40°C to +150°C, where T REF = 25°C and where the function ΔL(f x, f y, T) is defined as the difference L(f y, T)-L(f x, T), where L(f x, T) and L(f y, T) is the inductance, at a temperature T, of the common mode choke at a frequency f x and f y, respectively;