diff --git a/Project.toml b/Project.toml
index 717d8b366..6bdfc03c7 100644
--- a/Project.toml
+++ b/Project.toml
@@ -13,7 +13,7 @@ Symbolics = "0c5d862f-8b57-4792-8d23-62f2024744c7"
 IfElse = "0.1"
 ModelingToolkit = "8"
 OffsetArrays = "1"
-Symbolics = "0.1, 1, 2, 3, 4"
+Symbolics = "4.9"
 julia = "1.6"
 
 [extras]
diff --git a/src/Blocks/continuous.jl b/src/Blocks/continuous.jl
index 96bee5f69..7cb858f7e 100644
--- a/src/Blocks/continuous.jl
+++ b/src/Blocks/continuous.jl
@@ -111,7 +111,7 @@ Critical damping corresponds to `d=1`, which yields the fastest step response wi
 
 # Parameters:
 - `k`: Gain
-- `w`: Angular frequency
+- `w`: [`rad/s`] Angular frequency
 - `d`: Damping
 - `x_start`: Initial value of state (output)
 - `xd_start`: Initial value of derivative of state (output)
@@ -438,7 +438,7 @@ function StateSpace(; A, B, C, D = nothing, x_start = zeros(size(A, 1)), name)
     end
     @named input = RealInput(nin = nu)
     @named output = RealOutput(nout = ny)
-    @variables x[1:nx](t) = x_start
+    @variables x(t)[1:nx] = x_start
     # pars = @parameters A=A B=B C=C D=D # This is buggy
     eqs = [ # FIXME: if array equations work
         [Differential(t)(x[i]) ~ sum(A[i, k] * x[k] for k in 1:nx) +
diff --git a/src/Blocks/utils.jl b/src/Blocks/utils.jl
index 97b676125..5fd6c32f3 100644
--- a/src/Blocks/utils.jl
+++ b/src/Blocks/utils.jl
@@ -2,7 +2,7 @@
     if nin == 1
         @variables u(t)=u_start [input = true]
     else
-        @variables u[1:nin](t)=u_start [input = true]
+        @variables u(t)[1:nin]=u_start [input = true]
         u = collect(u)
     end
     ODESystem(Equation[], t, [u...], []; name = name)
@@ -24,7 +24,7 @@ Connector with one input signal of type Real.
     if nout == 1
         @variables u(t)=u_start [output = true]
     else
-        @variables u[1:nout](t)=u_start [output = true]
+        @variables u(t)[1:nout]=u_start [output = true]
         u = collect(u)
     end
     ODESystem(Equation[], t, [u...], []; name = name)
@@ -45,7 +45,7 @@ Connector with one output signal of type Real.
 """
     SISO(;name, u_start=0.0, y_start=0.0)
 
-Single Input Single Output continuous control block.
+Single input single output (SISO) continuous system block.
 
 # Parameters:
 - `u_start`: Initial value for the input
@@ -66,7 +66,7 @@ end
 """
     MIMO(;name, nin=1, nout=1, u_start=zeros(nin), y_start=zeros(nout))
 
-Base class for a multiple Input multiple Output continuous control block.
+Base class for a multiple input multiple output (MIMO) continuous system block.
 
 # Parameters:
 - `nin`: Input dimension
@@ -78,8 +78,8 @@ function MIMO(; name, nin = 1, nout = 1, u_start = zeros(nin), y_start = zeros(n
     @named input = RealInput(nin = nin, u_start = u_start)
     @named output = RealOutput(nout = nout, u_start = y_start)
     @variables begin
-        u[1:nin](t) = u_start
-        y[1:nout](t) = y_start
+        u(t)[1:nin] = u_start
+        y(t)[1:nout] = y_start
     end
     eqs = [
         [u[i] ~ input.u[i] for i in 1:nin]...,