How to change the first row of a matrix to be the same as an already programmed vector?

So I have vector x

 x= 2:4:18

I have the matrix M

 M= magic(5)
 M=
    17    24    18     8    15
    23     5     7     2    16
     4     6    13    20     6
    10    12    19    21     3
    11    14    25     2     9

I want the first row of M to be equal to x I write

 M(1,:)=x

but I get the error "The expression to the left of the equals sign is not a valid target for an assignment."

[Stephen23]

It works for me:

>> M = magic(5)
M =
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9
>> x = 2:4:18
x =
     2     6    10    14    18
>> M(1,:) = x
M =
     2     6    10    14    18
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9