diff --git a/src/dual.jl b/src/dual.jl
index 6d13dec3..48d5d0e3 100644
--- a/src/dual.jl
+++ b/src/dual.jl
@@ -625,7 +625,7 @@ end
 @generated function calc_fma_xyz(x::Dual{T,<:Any,N},
                                  y::Dual{T,<:Any,N},
                                  z::Dual{T,<:Any,N}) where {T,N}
-    ex = Expr(:tuple, [:(fma(value(x), partials(y)[$i], fma(value(y), partials(x)[$i], partials(z)[$i]))) for i in 1:N]...)
+    ex = Expr(:tuple, [:(_fma_partial(value(x), partials(y, $i), _fma_partial(value(y), partials(x, $i), partials(z, $i)))) for i in 1:N]...)
     return quote
         $(Expr(:meta, :inline))
         v = fma(value(x), value(y), value(z))
@@ -642,7 +642,7 @@ end
 @generated function calc_fma_xz(x::Dual{T,<:Any,N},
                                 y::Real,
                                 z::Dual{T,<:Any,N}) where {T,N}
-    ex = Expr(:tuple, [:(fma(partials(x)[$i], y,  partials(z)[$i])) for i in 1:N]...)
+    ex = Expr(:tuple, [:(_fma_partial(y, partials(x, $i), partials(z, $i))) for i in 1:N]...)
     return quote
         $(Expr(:meta, :inline))
         v = fma(value(x), y, value(z))
@@ -667,7 +667,7 @@ end
 @generated function calc_muladd_xyz(x::Dual{T,<:Any,N},
                                     y::Dual{T,<:Any,N},
                                     z::Dual{T,<:Any,N}) where {T,N}
-    ex = Expr(:tuple, [:(muladd(value(x), partials(y)[$i], muladd(value(y), partials(x)[$i], partials(z)[$i]))) for i in 1:N]...)
+    ex = Expr(:tuple, [:(_muladd_partial(value(x), partials(y, $i), _muladd_partial(value(y), partials(x, $i), partials(z, $i)))) for i in 1:N]...)
     return quote
         $(Expr(:meta, :inline))
         v = muladd(value(x), value(y), value(z))
@@ -684,7 +684,7 @@ end
 @generated function calc_muladd_xz(x::Dual{T,<:Any,N},
                                    y::Real,
                                    z::Dual{T,<:Any,N}) where {T,N}
-    ex = Expr(:tuple, [:(muladd(partials(x)[$i], y,  partials(z)[$i])) for i in 1:N]...)
+    ex = Expr(:tuple, [:(_muladd_partial(y, partials(x, $i), partials(z, $i))) for i in 1:N]...)
     return quote
         $(Expr(:meta, :inline))
         v = muladd(value(x), y, value(z))
diff --git a/src/partials.jl b/src/partials.jl
index 49f8364b..66a29b26 100644
--- a/src/partials.jl
+++ b/src/partials.jl
@@ -117,9 +117,19 @@ if NANSAFE_MODE_ENABLED
         y = partial / x
         return iszero(partial) ? zero(y) : y
     end
+    @inline function _fma_partial(x::Real, partial::Real, acc::Real)
+        y = fma(x, partial, acc)
+        return iszero(partial) ? oftype(y, acc) : y
+    end
+    @inline function _muladd_partial(x::Real, partial::Real, acc::Real)
+        y = muladd(x, partial, acc)
+        return iszero(partial) ? oftype(y, acc) : y
+    end
 else
     @inline _mul_partial(partial::Real, x::Real) = partial * x
     @inline _div_partial(partial::Real, x::Real) = partial / x
+    @inline _fma_partial(x::Real, partial::Real, acc::Real) = fma(x, partial, acc)
+    @inline _muladd_partial(x::Real, partial::Real, acc::Real) = muladd(x, partial, acc)
 end
 
 # edge cases where N == 0 #
diff --git a/test/DualTest.jl b/test/DualTest.jl
index 67d9c9f7..e7429be5 100644
--- a/test/DualTest.jl
+++ b/test/DualTest.jl
@@ -761,4 +761,18 @@ end
     end
 end
 
+@testset "fma and muladd: consistency with `x * y + z`" begin # issue #860
+    for f in (fma, muladd)
+        for (x, y, z) in (
+            (Dual{TestTag}(Inf, 0.0), Dual{TestTag}(2.0, 0.0), Dual{TestTag}(0.0, 1.0)),
+            (Dual{TestTag}(1.0, 0.0), Inf, Dual{TestTag}(0.0, 1.0)),
+            (Inf, Dual{TestTag}(1.0, 0.0), Dual{TestTag}(0.0, 1.0)),
+        )
+            d = f(x, y, z)
+            @test value(d) === Inf
+            @test isequal(d, x * y + z)
+        end
+    end
+end
+
 end # module