diff --git a/src/runestone.jl b/src/runestone.jl
index 592f407..3aee271 100644
--- a/src/runestone.jl
+++ b/src/runestone.jl
@@ -96,6 +96,7 @@ function format_float_literals(ctx::Context, node::JuliaSyntax.GreenNode)
     # Check and shortcut the happy path first
     r = r"""
     ^
+    (?:[+-])?            # Optional sign
     (?:(?:[1-9]\d*)|0)   # Non-zero followed by any digit, or just a single zero
     \.                   # Decimal point
     (?:(?:\d*[1-9])|0)   # Any digit with a final nonzero, or just a single zero
@@ -110,9 +111,13 @@ function format_float_literals(ctx::Context, node::JuliaSyntax.GreenNode)
         return nothing
     end
     # Split up the pieces
-    r = r"^(?<int>\d*)(?:\.?(?<frac>\d*))?(?:(?<epm>[eEf][+-]?)(?<exp>\d+))?$"
+    r = r"^(?<sgn>[+-])?(?<int>\d*)(?:\.?(?<frac>\d*))?(?:(?<epm>[eEf][+-]?)(?<exp>\d+))?$"
     m = match(r, str)
     io = IOBuffer() # TODO: Could be reused?
+    # Write the sign part
+    if (sgn = m[:sgn]; sgn !== nothing)
+        write(io, sgn)
+    end
     # Strip leading zeros from integral part
     int_part = isempty(m[:int]) ? "0" : m[:int]
     int_part = replace(int_part, r"^0*((?:[1-9]\d*)|0)$" => s"\1")
diff --git a/test/runtests.jl b/test/runtests.jl
index 714017f..b840c2c 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -79,13 +79,17 @@ end
         ["1f-3", "01f-3", "01.f-3", "1.f-3", "1.000f-3", "01.00f-3"] => "1.0f-3",
     ]
     mod = Module()
-    for (as, b) in test_cases
-        for a in as
-            c = Core.eval(mod, Meta.parse(a))
-            d = Core.eval(mod, Meta.parse(b))
-            @test c == d
-            @test typeof(c) == typeof(d)
-            @test format_string(a) == b
+    for prefix in ("", "-", "+")
+        for (as, b) in test_cases
+            b = prefix * b
+            for a in as
+                a = prefix * a
+                c = Core.eval(mod, Meta.parse(a))
+                d = Core.eval(mod, Meta.parse(b))
+                @test c == d
+                @test typeof(c) == typeof(d)
+                @test format_string(a) == b
+            end
         end
     end
 end