The present invention provides a glass fiber strand comprising at least one glass fiber at least partially coated with a sizing composition prepared from ingredients comprising; at least one starch; at least one lubricant; and at least one silane coupling agent comprising: [((R1)bY)aR23-aSiR3]2NX, wherein R1 and R2 are each monovalent radials; R3 is a divalent linking group; a is 1 to 3; X is (R4)bZC(═O)CH(Q)CH(Q)—, wherein Z is CH2, O, S or N, Q is H, alkyl, aryl, alkaryl, or C(═O)ZR4 and R4 is a hydrocarbon moiety of one to twenty carbon atoms, hydrogen, a silyl group or an organic polymer; Y is oxygen, nitrogen or sulfur; and b is 1 or 2 depending upon the valency of Y. In one particular embodiment of the invention, the silane in the aqueous sizing composition is (CH3)3COC(═O)CH2CH2N[CH2CH2CH2Si(OCH3)3]2.