diff --git a/math-core/src/latex_parser/parse.rs b/math-core/src/latex_parser/parse.rs
index bbcb07a..18ddeff 100644
--- a/math-core/src/latex_parser/parse.rs
+++ b/math-core/src/latex_parser/parse.rs
@@ -705,7 +705,12 @@ where
                 } else if matches!(
                     self.peek.token(),
                     Token::Relation(_) | Token::Punctuation(_) | Token::Colon
-                ) {
+                ) || (prev_state.real_boundaries
+                    && matches!(
+                        self.peek.token(),
+                        Token::Eof | Token::GroupEnd | Token::End | Token::Right
+                    ))
+                {
                     Some(MathSpacing::Zero)
                 } else {
                     Some(MathSpacing::FiveMu)
diff --git a/math-core/src/lib.rs b/math-core/src/lib.rs
index 374e518..13b57b6 100644
--- a/math-core/src/lib.rs
+++ b/math-core/src/lib.rs
@@ -461,6 +461,8 @@ mod tests {
             ("colon_fusion", r"a := 2 \land b :\equiv 3"),
             ("double_colon", r"a :: b"),
             ("colon_first_group", r"x{:x}"),
+            ("colon_last_group", r"{x:}x"),
+            ("colon_alone_group", r"x{:}x"),
             ("colon_approx", r"x:\approx 2"),
             ("colon_sqrt", r"\sqrt :"),
             (
diff --git a/math-core/src/snapshots/math_core__tests__colon_alone_group.snap b/math-core/src/snapshots/math_core__tests__colon_alone_group.snap
new file mode 100644
index 0000000..459634a
--- /dev/null
+++ b/math-core/src/snapshots/math_core__tests__colon_alone_group.snap
@@ -0,0 +1,9 @@
+---
+source: math-core/src/lib.rs
+expression: "x{:}x"
+---
+<math>
+    <mi>x</mi>
+    <mo lspace="0" rspace="0">:</mo>
+    <mi>x</mi>
+</math>
diff --git a/math-core/src/snapshots/math_core__tests__colon_last_group.snap b/math-core/src/snapshots/math_core__tests__colon_last_group.snap
new file mode 100644
index 0000000..90ee815
--- /dev/null
+++ b/math-core/src/snapshots/math_core__tests__colon_last_group.snap
@@ -0,0 +1,11 @@
+---
+source: math-core/src/lib.rs
+expression: "{x:}x"
+---
+<math>
+    <mrow>
+        <mi>x</mi>
+        <mo lspace="0.2778em" rspace="0">:</mo>
+    </mrow>
+    <mi>x</mi>
+</math>