fix

Author: vyudu

src/utils.jl

@@ -156,9 +156,12 @@ function check_variables(dvs, iv)
 end
 
 function check_var_types(sys_type::Type{T}, dvs) where T <: AbstractSystem
-    any(u -> !(symtype(u) <: Number), dvs) && error("The type of unknown variables must be a numeric type.")
-    if sys_type == ODESystem || sys_type == SDESystem || sys_type == PDESystem
-        any(u -> !(symtype(u) <: AbstractFloat), dvs) && error("The type of unknown variables for an SDESystem, PDESystem, or ODESystem must be a float.")
+    if any(u -> !(symtype(u) <: Number), dvs) 
+        error("The type of unknown variables must be a numeric type.")
+    elseif any(u -> (symtype(u) !== symtype(dvs[1])), dvs) 
+        error("The type of all the unknown variables in a system must all be the same.")
+    elseif sys_type == ODESystem || sys_type == SDESystem || sys_type == PDESystem
+        any(u -> !(symtype(u) == Real), dvs) && error("The type of unknown variables for an SDESystem, PDESystem, or ODESystem should not be a concrete numeric type.")
     end
     nothing
 end