diff --git a/src/chisels.jl b/src/chisels.jl
index ee2ac95..b556e71 100644
--- a/src/chisels.jl
+++ b/src/chisels.jl
@@ -490,7 +490,7 @@ function has_newline_after_non_whitespace(node::Node)
         kids = verified_kids(node)
         idx = findlast(!JuliaSyntax.is_whitespace, kids)
         if idx === nothing
-            @assert false
+            unreachable()
             # Everything is whitespace...
             return any(x -> kind(x) === K"NewlineWs", kids)
         end
diff --git a/src/debug.jl b/src/debug.jl
index d9f4644..77400ea 100644
--- a/src/debug.jl
+++ b/src/debug.jl
@@ -16,7 +16,7 @@ end
 function Base.showerror(io::IO, err::AssertionError)
     print(
         io,
-        "Runic.AssertionError: `", err.msg, "`. This is unexpected, " *
+        "Runic.AssertionError: ", err.msg, ". This is unexpected, " *
             "please file an issue with a reproducible example at " *
             "https://github.com/fredrikekre/Runic.jl/issues/new."
     )
@@ -27,3 +27,5 @@ function macroexpand_assert(expr)
     msg = string(expr)
     return :($(esc(expr)) || throw(AssertionError($msg)))
 end
+
+@noinline unreachable() = throw(AssertionError("unreachable code reached"))
diff --git a/src/runestone.jl b/src/runestone.jl
index 16bb83e..20e1aaf 100644
--- a/src/runestone.jl
+++ b/src/runestone.jl
@@ -543,7 +543,7 @@ function spaces_in_listlike(ctx::Context, node::Node)
                     accept_node!(ctx, kid′)
                     any_kid_changed && push!(kids′, kid′)
                 else
-                    @assert false # Unreachable?
+                    unreachable()
                 end
                 # Transition to the next state
                 state = before_last_item ? (:expect_space) : (:expect_closing)
@@ -660,7 +660,7 @@ function spaces_in_listlike(ctx::Context, node::Node)
                 # K"parameters"...
                 state = i == last_item_idx ? (:expect_closing) : (:expect_item)
             else
-                @assert false # Unreachable?
+                unreachable()
             end
         elseif state === :expect_space
             if (kind(kid′) === K"Whitespace" && span(kid′) == 1) ||
@@ -759,7 +759,7 @@ function spaces_in_listlike(ctx::Context, node::Node)
                 accept_node!(ctx, kid′)
                 any_kid_changed && push!(kids′, kid′)
             else
-                @assert false # Unreachable?
+                unreachable()
             end
         end # if-state
         any_kid_changed |= this_kid_changed
@@ -780,7 +780,7 @@ function spaces_in_listlike(ctx::Context, node::Node)
             accept_node!(ctx, comma)
             state = :expect_closing
         else
-            @assert false # Unreachable?
+            unreachable()
         end
     end
     @assert state === :expect_closing
@@ -896,7 +896,7 @@ function no_spaces_around_x(ctx::Context, node::Node, is_x::F) where {F}
                     # Remove trailing whitespace
                     ws_kid = last_leaf(kid)
                     if kind(ws_kid) === K"Whitespace"
-                        @assert false # Hope this doesn't happen often...
+                        unreachable()
                     end
                 end
             end
@@ -994,7 +994,7 @@ function spaces_in_export_public(ctx::Context, node::Node)
                 accept_node!(ctx, kid)
                 state = :expect_space
             else
-                @assert false
+                unreachable()
             end
         else
             @assert state === :expect_comma
@@ -1011,7 +1011,7 @@ function spaces_in_export_public(ctx::Context, node::Node)
                 end
                 state = :expect_comma
             else
-                @assert false
+                unreachable()
             end
         end
         i += 1
@@ -1331,7 +1331,7 @@ function spaces_around_keywords(ctx::Context, node::Node)
                     push!(kids′, kid′)
                 end
             elseif !space_after && kind(last_leaf(kid)) === K"Whitespace"
-                @assert false # Unreachable?
+                unreachable()
             else
                 # Reachable in e.g. `T where{T}`, `if(`, ... insert space
                 @assert kind(node) in KSet"where if elseif while do function return local global module baremodule"