diff --git a/src/sage/numerical/backends/generic_backend.pyx b/src/sage/numerical/backends/generic_backend.pyx
index 69ef5bb389c..6dd85a01d9d 100644
--- a/src/sage/numerical/backends/generic_backend.pyx
+++ b/src/sage/numerical/backends/generic_backend.pyx
@@ -96,12 +96,12 @@ cdef class GenericBackend:
         """
         raise NotImplementedError()
 
-    cpdef int add_variables(self, int n, lower_bound=0, upper_bound=None, binary=False, continuous=True, integer=False, obj=None, names=None) except -1:
+    cpdef int add_variables(self, int n, lower_bound=False, upper_bound=None, binary=False, continuous=True, integer=False, obj=None, names=None) except -1:
         """
         Add ``n`` variables.
 
         This amounts to adding new columns to the matrix. By default,
-        the variables are both positive and real.
+        the variables are both nonnegative and real.
 
         INPUT:
 
@@ -151,6 +151,10 @@ cdef class GenericBackend:
         """
         cdef int i
         cdef int value
+        if lower_bound is False:
+            lower_bound = self.zero()
+        if obj is None:
+            obj = self.zero()
         for i in range(n):
             value = self.add_variable(lower_bound = lower_bound,
                                       upper_bound = upper_bound,
diff --git a/src/sage/numerical/backends/gurobi_backend.pyx b/src/sage/numerical/backends/gurobi_backend.pyx
index 574be69f48e..72d4f595808 100644
--- a/src/sage/numerical/backends/gurobi_backend.pyx
+++ b/src/sage/numerical/backends/gurobi_backend.pyx
@@ -172,72 +172,6 @@ cdef class GurobiBackend(GenericBackend):
 
         return self.ncols()-1
 
-    cpdef int add_variables(self, int number, lower_bound=0.0, upper_bound=None, binary=False, continuous=False, integer=False, obj=0.0, names=None) except -1:
-        """
-        Add ``number`` new variables.
-
-        This amounts to adding new columns to the matrix. By default,
-        the variables are both positive, real and theor coefficient in
-        the objective function is 0.0.
-
-        INPUT:
-
-        - ``n`` - the number of new variables (must be > 0)
-
-        - ``lower_bound`` - the lower bound of the variable (default: 0)
-
-        - ``upper_bound`` - the upper bound of the variable (default: ``None``)
-
-        - ``binary`` - ``True`` if the variable is binary (default: ``False``).
-
-        - ``continuous`` - ``True`` if the variable is binary (default: ``True``).
-
-        - ``integer`` - ``True`` if the variable is binary (default: ``False``).
-
-        - ``obj`` - (optional) coefficient of all variables in the objective function (default: 0.0)
-
-        - ``names`` - optional list of names (default: ``None``)
-
-        OUTPUT: The index of the variable created last.
-
-        EXAMPLE::
-
-            sage: from sage.numerical.backends.generic_backend import get_solver           # optional - Gurobi
-            sage: p = get_solver(solver = "Gurobi")                                        # optional - Gurobi
-            sage: p.ncols()                                                                # optional - Gurobi
-            0
-            sage: p.add_variables(5)                                                       # optional - Gurobi
-            4
-            sage: p.ncols()                                                                # optional - Gurobi
-            5
-            sage: p.add_variables(2, lower_bound=-2.0, integer=True, obj=42.0, names=['a','b']) # optional - Gurobi
-            6
-
-        TESTS:
-
-        Check that arguments are used::
-
-            sage: p.col_bounds(5) # tol 1e-8, optional - Gurobi
-            (-2.0, None)
-            sage: p.is_variable_integer(5)   # optional - Gurobi
-            True
-            sage: p.col_name(5)              # optional - Gurobi
-            'a'
-            sage: p.objective_coefficient(5) # tol 1e-8, optional - Gurobi
-            42.0
-        """
-        cdef int i
-        cdef int value
-        for i in range(number):
-            value = self.add_variable(lower_bound = lower_bound,
-                              upper_bound = upper_bound,
-                              binary = binary,
-                              continuous = continuous,
-                              integer = integer,
-                              obj = obj,
-                              name = None if names is None else names[i])
-        return value
-
     cpdef set_variable_type(self, int variable, int vtype):
         """
         Set the type of a variable