diff --git a/src/ALL_fortran.cpp b/src/ALL_fortran.cpp
index c20e219ee95f393c6ac87c611b965d33d37d0109..36f46c31d0e622db2dbfd88fba1883cf7879e3bc 100644
--- a/src/ALL_fortran.cpp
+++ b/src/ALL_fortran.cpp
@@ -178,7 +178,7 @@ void all_balance_c(ALL_t *all_obj) {
   ALL_catch
 }
 
-double all_get_gamma_c(ALL_t *all_obj, double *gamma) { *gamma =  all_obj->getGamma(); }
+void all_get_gamma_c(ALL_t *all_obj, double *gamma) { *gamma =  all_obj->getGamma(); }
 
 // wrapper to get number of new vertices
 void all_get_number_of_vertices_c(ALL_t *all_obj, int *n_vertices) {