diff --git a/src/simpleweighteddigraph.jl b/src/simpleweighteddigraph.jl
index 7c41c26..e160f9b 100644
--- a/src/simpleweighteddigraph.jl
+++ b/src/simpleweighteddigraph.jl
@@ -163,10 +163,9 @@ Graphs.inneighbors(g::SimpleWeightedDiGraph, v::Integer) = g.weights[v, :].nzind
 # add_edge! will overwrite weights.
 function Graphs.add_edge!(g::SimpleWeightedDiGraph, e::SimpleWeightedGraphEdge)
     T = eltype(g)
-    U = weighttype(g)
     s_, d_, w = Tuple(e)
 
-    if w == zero(U)
+    if iszero(w)
         @warn "Note: adding edges with a zero weight to this graph type has no effect." maxlog =
             1 _id = :swd_add_edge_zero
         return false
diff --git a/src/simpleweightedgraph.jl b/src/simpleweightedgraph.jl
index bfc990e..c6018f6 100644
--- a/src/simpleweightedgraph.jl
+++ b/src/simpleweightedgraph.jl
@@ -175,10 +175,9 @@ Graphs.inneighbors(g::SimpleWeightedGraph, x...) = outneighbors(g, x...)
 # add_edge! will overwrite weights.
 function Graphs.add_edge!(g::SimpleWeightedGraph, e::SimpleWeightedGraphEdge)
     T = eltype(g)
-    U = weighttype(g)
     s_, d_, w = Tuple(e)
 
-    if w == zero(U)
+    if iszero(w)
         @warn "Note: adding edges with a zero weight to this graph type has no effect." maxlog =
             1 _id = :swg_add_edge_zero
         return false