diff --git a/src/JuliaSyntaxHighlighting.jl b/src/JuliaSyntaxHighlighting.jl
index 48ad0df..2de62dc 100644
--- a/src/JuliaSyntaxHighlighting.jl
+++ b/src/JuliaSyntaxHighlighting.jl
@@ -148,13 +148,13 @@ function paren_type(k::Kind)
 end
 
 mutable struct ParenDepthCounter
-    paren::UInt
-    bracket::UInt
-    curly::UInt
+    paren::Int
+    bracket::Int
+    curly::Int
 end
 
 ParenDepthCounter() =
-    ParenDepthCounter(zero(UInt), zero(UInt), zero(UInt))
+    ParenDepthCounter(0, 0, 0)
 
 struct GreenLineage{H}
     node::GreenNode{H}
@@ -345,7 +345,7 @@ function _hl_annotations!(highlights::Vector{@NamedTuple{region::UnitRange{Int},
             setfield!(pdepths, ptype, depthref + depthchange)
         else
             depth0 = getfield(pdepths, ptype)
-            setfield!(pdepths, ptype, depthref + depthchange)
+            setfield!(pdepths, ptype, max(0, depthref + depthchange))
             depth0
         end
         if pdepth <= 0 && UNMATCHED_DELIMITERS_ENABLED[]
diff --git a/test/runtests.jl b/test/runtests.jl
index 05bc070..74db56b 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -27,3 +27,12 @@ astr_sum1to8 = Base.AnnotatedString("sum(1:8)")
 
 # Check for string indexing issues
 @test Base.annotations(highlight(":π")) |> first |> first == 1:3
+
+# Test unpaired parentheses (issue #17)
+# Test consecutive unpaired closing parens and that depth counter resets properly
+reset_after_unpaired = highlight("(()))) ()")
+anns = Base.annotations(reset_after_unpaired)
+@test anns[5].value == :julia_unpaired_parentheses  # First unpaired
+@test anns[6].value == :julia_unpaired_parentheses  # Second unpaired
+@test anns[7].value == :julia_rainbow_paren_1       # Opening after reset
+@test anns[8].value == :julia_rainbow_paren_1       # Closing after reset