diff --git a/src/systems/diffeqs/abstractodesystem.jl b/src/systems/diffeqs/abstractodesystem.jl
index c7cc7398a8..0aa1820ddb 100644
--- a/src/systems/diffeqs/abstractodesystem.jl
+++ b/src/systems/diffeqs/abstractodesystem.jl
@@ -1564,11 +1564,12 @@ function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
                merge(todict(parammap), Dict(get_iv(sys) => t))
     u0map = isempty(u0map) ? Dict() : todict(u0map)
     guesses = isempty(guesses) ? Dict() : todict(guesses)
+    defaults = defaults(isys)
 
     # Check that all unknowns have guesses
     # TODO: which, if any, unknowns should be excluded from this guess?
     for x in unknowns(isys)
-        x in keys(guesses) || throw(ArgumentError("Missing guess for $x."))
+        x in keys(guesses) || x in keys(defaults) || throw(ArgumentError("Missing guess for $x."))
     end
 
     u0map = merge(guesses, u0map)