diff --git a/src/aff_expr.jl b/src/aff_expr.jl
index 53fe7d91581..e4ad815f32a 100644
--- a/src/aff_expr.jl
+++ b/src/aff_expr.jl
@@ -17,9 +17,12 @@
 
 # Utilities for OrderedDict
 function _add_or_set!(dict::OrderedDict{K,V}, k::K, v::V) where {K,V}
+    # Adding zero terms to this dictionary leads to unacceptable performance
+    # degradations. See, e.g., https://github.com/JuliaOpt/JuMP.jl/issues/1946.
+    if iszero(v)
+        return dict  # No-op.
+    end
     # TODO: This unnecessarily requires two lookups for k.
-    # TODO: Decide if we want to drop zeros here after understanding the
-    # performance implications.
     dict[k] = get!(dict, k, zero(V)) + v
     return dict
 end
diff --git a/test/expr.jl b/test/expr.jl
index 796a319a34c..2a8005e77bb 100644
--- a/test/expr.jl
+++ b/test/expr.jl
@@ -25,12 +25,12 @@ function expressions_test(ModelType::Type{<:JuMP.AbstractModel}, VariableRefType
     @testset "drop_zeros!(::GenericAffExpr)" begin
         m = ModelType()
         @variable(m, x[1:2])
-        expr = x[1] + 0.0 * x[2] + 1
+        expr = x[1] + x[2] - x[2] + 1
         @test !isequal(expr, x[1] + 1)
         JuMP.drop_zeros!(expr)
         @test isequal(expr, x[1] + 1)
     end
-  
+
     @testset "iszero(::GenericAffExpr)" begin
         m = ModelType()
         @variable(m, x)
@@ -55,12 +55,12 @@ function expressions_test(ModelType::Type{<:JuMP.AbstractModel}, VariableRefType
     @testset "drop_zeros!(::GenericQuadExpr)" begin
         m = ModelType()
         @variable(m, x[1:2])
-        expr = x[1]^2 + 0.0 * x[2]^2 + x[1] + 0.0 * x[2] + 1
+        expr = x[1]^2 + x[2]^2 - x[2]^2 + x[1] + x[2] - x[2] + 1
         @test !isequal(expr, x[1]^2 + x[1] + 1)
         JuMP.drop_zeros!(expr)
         @test isequal(expr, x[1]^2 + x[1] + 1)
     end
-  
+
     @testset "iszero(::GenericQuadExpr)" begin
         m = ModelType()
         @variable(m, x)