diff --git a/c/interaction/interaction.c b/c/interaction/interaction.c
index d0d6268..54c55bb 100644
--- a/c/interaction/interaction.c
+++ b/c/interaction/interaction.c
@@ -30,12 +30,12 @@ interaction_ufunc_force
 	, void * data)
 {
 	char * in = args[0]
-		, * out = args[1]
-		, * raw_coefficients = args[2];
+		, * raw_coefficients = args[1]
+		, * out = args[2];
 	npy_intp n = dimensions[0];
 	npy_intp in_step = steps[0]
-		, out_step = steps[1]
-		, raw_coefficients_steps = steps[2];
+		, raw_coefficients_steps = steps[1]
+		, out_step = steps[2];
 
 	npy_intp i;