diff --git a/src/compile_error_kind.rs b/src/compile_error_kind.rs
index 49b5624d..36a98437 100644
--- a/src/compile_error_kind.rs
+++ b/src/compile_error_kind.rs
@@ -66,7 +66,7 @@ pub(crate) enum CompileErrorKind<'src> {
   FunctionArgumentCountMismatch {
     function: &'src str,
     found: usize,
-    expected: Range<usize>,
+    expected: RangeInclusive<usize>,
   },
   Include,
   InconsistentLeadingWhitespace {
diff --git a/src/function.rs b/src/function.rs
index dbce9349..f741b5e4 100644
--- a/src/function.rs
+++ b/src/function.rs
@@ -108,15 +108,15 @@ pub(crate) fn get(name: &str) -> Option<Function> {
 }
 
 impl Function {
-  pub(crate) fn argc(&self) -> Range<usize> {
+  pub(crate) fn argc(&self) -> RangeInclusive<usize> {
     match *self {
-      Nullary(_) => 0..0,
-      Unary(_) => 1..1,
-      UnaryOpt(_) => 1..2,
-      UnaryPlus(_) => 1..usize::MAX,
-      Binary(_) => 2..2,
-      BinaryPlus(_) => 2..usize::MAX,
-      Ternary(_) => 3..3,
+      Nullary(_) => 0..=0,
+      Unary(_) => 1..=1,
+      UnaryOpt(_) => 1..=2,
+      UnaryPlus(_) => 1..=usize::MAX,
+      Binary(_) => 2..=2,
+      BinaryPlus(_) => 2..=usize::MAX,
+      Ternary(_) => 3..=3,
     }
   }
 }
diff --git a/src/parser.rs b/src/parser.rs
index b1d088e9..90389a29 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -2568,7 +2568,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "arch",
       found: 1,
-      expected: 0..0,
+      expected: 0..=0,
     },
   }
 
@@ -2582,7 +2582,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "env_var",
       found: 0,
-      expected: 1..1,
+      expected: 1..=1,
     },
   }
 
@@ -2596,7 +2596,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "env",
       found: 3,
-      expected: 1..2,
+      expected: 1..=2,
     },
   }
 
@@ -2610,7 +2610,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "env",
       found: 0,
-      expected: 1..2,
+      expected: 1..=2,
     },
   }
 
@@ -2624,7 +2624,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "env_var_or_default",
       found: 1,
-      expected: 2..2,
+      expected: 2..=2,
     },
   }
 
@@ -2638,7 +2638,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "join",
       found: 1,
-      expected: 2..usize::MAX,
+      expected: 2..=usize::MAX,
     },
   }
 
@@ -2652,7 +2652,7 @@ mod tests {
     kind: FunctionArgumentCountMismatch {
       function: "replace",
       found: 1,
-      expected: 3..3,
+      expected: 3..=3,
     },
   }
 }
diff --git a/src/range_ext.rs b/src/range_ext.rs
index bf4995e8..4773d22b 100644
--- a/src/range_ext.rs
+++ b/src/range_ext.rs
@@ -10,16 +10,14 @@ pub(crate) trait RangeExt<T> {
 
 pub(crate) struct DisplayRange<T>(T);
 
-impl Display for DisplayRange<&Range<usize>> {
+impl Display for DisplayRange<&RangeInclusive<usize>> {
   fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-    if self.0.start == self.0.end {
-      write!(f, "0")?;
-    } else if self.0.start == self.0.end - 1 {
-      write!(f, "{}", self.0.start)?;
-    } else if self.0.end == usize::MAX {
-      write!(f, "{} or more", self.0.start)?;
+    if self.0.start() == self.0.end() {
+      write!(f, "{}", self.0.start())?;
+    } else if *self.0.end() == usize::MAX {
+      write!(f, "{} or more", self.0.start())?;
     } else {
-      write!(f, "{} to {}", self.0.start, self.0.end - 1)?;
+      write!(f, "{} to {}", self.0.start(), self.0.end())?;
     }
     Ok(())
   }
@@ -76,10 +74,10 @@ mod tests {
     assert!(!(1..1).contains(&1));
     assert!((1..1).is_empty());
     assert!((5..5).is_empty());
-    assert_eq!((1..1).display().to_string(), "0");
-    assert_eq!((1..2).display().to_string(), "1");
-    assert_eq!((5..6).display().to_string(), "5");
-    assert_eq!((5..10).display().to_string(), "5 to 9");
-    assert_eq!((1..usize::MAX).display().to_string(), "1 or more");
+    assert_eq!((0..=0).display().to_string(), "0");
+    assert_eq!((1..=1).display().to_string(), "1");
+    assert_eq!((5..=5).display().to_string(), "5");
+    assert_eq!((5..=9).display().to_string(), "5 to 9");
+    assert_eq!((1..=usize::MAX).display().to_string(), "1 or more");
   }
 }
diff --git a/tests/functions.rs b/tests/functions.rs
index 68f8640b..8fc81aca 100644
--- a/tests/functions.rs
+++ b/tests/functions.rs
@@ -1050,3 +1050,21 @@ fn is_dependency() {
     .stdout("beta false\ngamma true\n")
     .run();
 }
+
+#[test]
+fn unary_argument_count_mismamatch_error_message() {
+  Test::new()
+    .justfile("x := datetime()")
+    .args(["--evaluate"])
+    .stderr(
+      "
+      error: Function `datetime` called with 0 arguments but takes 1
+       ——▶ justfile:1:6
+        │
+      1 │ x := datetime()
+        │      ^^^^^^^^
+      ",
+    )
+    .status(EXIT_FAILURE)
+    .run();
+}