diff --git a/src/lambdify.jl b/src/lambdify.jl
index 77e2217..06a0d0d 100644
--- a/src/lambdify.jl
+++ b/src/lambdify.jl
@@ -43,34 +43,34 @@ __ZERO__(xs...) = 0
 __HEAVISIDE__ = (a...)  -> (a[1] < 0 ? 0 : (a[1] > 0 ? 1 : (length(a) > 1 ? a[2] : NaN)))
 #  __SYMPY__ALL__,
 fn_map = Dict(
-              "Add" => :+,
-              "Sub" => :-,
-              "Mul" => :*, # :(SymPy.__PROD__)
-              "Div" => :/,
-              "Pow" => :^,
-              "re"  => :real,
-              "im"  => :imag,
-              "Abs" => :abs,
-              "Min" => :min,
-              "Max" => :max,
-              "Poly" => :identity,
-              "Piecewise" => :(SymPy._piecewise),
-              "Order" => :(SymPy.__ZERO__), # :(as...) -> 0,
-              "And" => :(SymPy.__ALL__), #:((as...) -> all(as)), #:(&),
-              "Or" =>  :(SymPy.__ANY__), #:((as...) -> any(as)), #:(|),
-              "Less" => :(<),
-              "LessThan" => :(<=),
-              "StrictLessThan" => :(<),
-              "Equal" => :(==),
-              "Equality" => :(==),
-              "Unequality" => :(!==),
-              "StrictGreaterThan" => :(>),
-              "GreaterThan" => :(>=),
-              "Greater" => :(>),
+    "Add" => :+,
+    "Sub" => :-,
+    "Mul" => :*, # :(SymPy.__PROD__)
+    "Div" => :/,
+    "Pow" => :^,
+    "re"  => :real,
+    "im"  => :imag,
+    "Abs" => :abs,
+    "Min" => :min,
+    "Max" => :max,
+    "Poly" => :identity,
+    "Piecewise" => :(SymPy._piecewise),
+    "Order" => :(SymPy.__ZERO__), # :(as...) -> 0,
+    "And" => :(SymPy.__ALL__), #:((as...) -> all(as)), #:(&),
+    "Or" =>  :(SymPy.__ANY__), #:((as...) -> any(as)), #:(|),
+    "Less" => :(<),
+    "LessThan" => :(<=),
+    "StrictLessThan" => :(<),
+    "Equal" => :(==),
+    "Equality" => :(==),
+    "Unequality" => :(!==),
+    "StrictGreaterThan" => :(>),
+    "GreaterThan" => :(>=),
+    "Greater" => :(>),
     "conjugate" => :conj,
     "atan2" => :atan,
-    "Heaviside" => :(SymPy.__HEAVISIDE__)
-              )
+    "Heaviside" => :(SymPy.__HEAVISIDE__),
+)
 
 map_fn(key, fn_map) = haskey(fn_map, key) ? fn_map[key] : Symbol(key)
 
@@ -89,7 +89,7 @@ function walk_expression(ex; values=Dict(), fns=Dict())
         return walk_expression(rhs(ex), values=values, fns=fns)
     end
 
-    if fn == "Symbol" || fn == "Dummy"
+    if fn == "Symbol" || fn == "Dummy" || fn == "IndexedBase"
         str_ex = string(ex)
         return get(vals_map, str_ex, Symbol(str_ex))
     elseif fn in ["Integer" , "Float"]
@@ -104,6 +104,8 @@ function walk_expression(ex; values=Dict(), fns=Dict())
         return (val, walk_expression(cond, values=values, fns=fns))
     elseif fn == "Tuple"
         return walk_expression.(Introspection.args(ex), values=values, fns=fns)
+    elseif fn == "Indexed"
+        return Expr(:ref, [walk_expression(a, values=values, fns=fns) for a in Introspection.args(ex)]...)
     elseif haskey(vals_map, fn)
         return vals_map[fn]
     end
diff --git a/test/tests.jl b/test/tests.jl
index 0d69552..2af11f4 100644
--- a/test/tests.jl
+++ b/test/tests.jl
@@ -809,3 +809,5 @@ end
     @test limit(ceil(x), x=>0, dir="+") != limit(ceil(x), x=>0, dir="-")
     @test limit(floor(x), x=>0, dir="+") != limit(floor(x), x=>0, dir="-")
 end
+
+@test SymPy.convert_expr(sympy.Indexed(sympy.IndexedBase(:x), 1, -2)) == :(x[1, -2])